BMW 4 Series vs Mercedes-Benz SL-Class

What's the difference?

The BMW M440i xDrive Gran Coupe manages to combine sleek design with a fun-to-drive personality and surprising practicality. It’s a rapid premium, four-door, five-seater offering extra flair, and in this part of the market, good value. But more than anything else it’s got a cracking in-line six under the bonnet.

The SL's overall score is somewhat skewed by everyday concerns, and rules are rules - an average punter will find the price of this car somewhat confusing and the devil-may-care attitude to fuel consumption bewildering.

If neither of these things are a problem, then the SL63 makes plenty of - well, not sense, because it's not a particularly clever or considered car - but it fills a niche that not so long ago we all thought would go the way of the dodo.

The fact it sells so few examples is betrayed by some of the cabin amenities and the fact that Mercedes hasn't put much effort into reducing the car's weight to improve its consumption or sharpen up the handling.

The fact it still exists at all is pretty damn cool, though, and for certain people an SL63 purchase is the culmination of a lot of hard work.

If it is your dream car, the SL63 won't disappoint. Everyone who rode with me said it was mightily impressive, but you've got to really want it. When you're not far off buying a Ferrari California T or Aston Martin V12 Vantage S for the money, you'll need a real yearning for the three-pointed star to go this way. And if you do, good luck to you - you've probably worked quite hard to get here.

So, how does this four-door 4 Series differ from a four-door 3 Series? The answer is as plain as the nose on this car’s face.

BMW’s head of design, Adrian van Hooydonk, has been expanding the brand’s signature ‘kidney grille’ in every conceivable direction, and this is the much talked about interpretation adorning all 4 Series models (petrol, hybrid and electric) as well as the M3 sedan.

The new Gran Coupe is longer, wider, and taller than the outgoing model, and the track is broader, front and rear. The wheelbase has also been extended, now a whole 5.0mm longer than the 3 Series.

The DRLs and headlight main beams are LED with laser high beams, immense gills square up the edges of the front clip, while a vent and the strake attached to it stand the car apart. Plus, of course, the doors are frameless. 

One niggle, though. I’m not in love with the slender door handles. It’s hard to get a good grip on them, especially in the wet. 

Standard 19-inch alloy rims are shod with Pirelli P Zero rubber 245/40 fr / 255/40 rr), the roofline slopes distinctly towards the rear, a lip spoiler on the trailing edge of the tailgate is classic BMW, darkened LED tail-lights wrap around the rear corner, and a diffuser-type panel is flanked by large exhaust apertures.

Our car’s ‘Aventurine Red’ finish is a $3850 option, but to my eyes anyway it looks superb.

Exterior trim including the grille frame, front air intake inserts, mirror upper housing, model designation badges, and tailpipe are finished in ‘Cerium Grey’, which I reckon 99.9 per cent of people will see as black. 

The interior will be familiar territory for any current BMW owner, the 12.3-inch digital instrument screen sitting in a compact, hooded binnacle, and partnering with a 10.25-inch multimedia display standing proud of the dash above the broad centre stack. 

The seats are trimmed in top-shelf leather with blue contrast stitching, plus the grippy sports wheel is also wrapped in genuine hide.

BMW calls the finish on the main buttons and controls ‘Galvanic’ which translates to a slick silver metallic look and feel. Configurable ambient interior lighting is a nice touch, and the broad console enhances the driver-focused feel, with a sprinkling of carbon-fibre around the centre console and dash lifting the sense of occasion.

Overall, the interior feels clean and classy with an obvious attention to detail.  

The SL has always been completely unapologetic about its size and seems to be designed to accentuate rather than hide its length and width. The long bonnet screams power and prestige, and get out of my way, and is reminiscent of the little-loved McLaren SLR project of some years ago.

The size of the Mercedes logo on the huge front grille leaves you in little doubt about the brand of car that’s about to pass you at speed and some might say (okay, I would) that its large surface area is a little vulgar.

Like the SLR, the design doesn't seem to have a particularly cohesive strategy, with a number of Mercedes elements from around the traps that climb over each other. Roof up it looks awkward because of the gigantic posterior while with the roof down it looks overly long and, again, tail-heavy.

Folding hardtops are notoriously cumbersome and need a lot of room to hide them, but the silent operation is something to behold.

Elements that are worth deleting if possible are the dodgy 'Biturbo' badges. It's that kind of bling that gets people raising their little finger at you.

At close to 4.8m long the 4 Series Gran Coupe is a sizeable machine. Up front, the feeling is airy and comfortable, and the rear is surprisingly spacious, especially in light of the car's sloping roofline.

At 183cm I have to fold myself tightly to fit under the low roof, but once inside I have enough room to sit behind the driver’s seat set for my position with more than enough legroom and adequate headroom. Put three full-size adults across the back row, though, and there will be breathing difficulties.

Kids will be fine, however, and individual vents with adjustable temp in the rear was a big plus during a particularly hot test week.

For storage there are generous door bins in the front with room for large bottles, a decent glove box, dual cupholders in the centre console, a reasonable lidded bin (which doubles as a centre armrest), and the wireless device charging bay (forward of the gearshift) makes a handy oddments space when not in use.

In the rear, again the doors feature pockets with room for (medium-size) bottles, there’s a fold down centre armrest with two cupholders, but thanks to the one-piece shells on our test car’s optional M Sport front seats there are no map pockets.

Power and connectivity runs to a USB-A socket and a 12V outlet in the front centre console, as well a USB-C port in the front storage bin, a pair of USB-Cs in the rear, and a 12V outlet in the boot.

Speaking of which, lift the tailgate and with the rear seat upright we were able to fit all three of our suitcases or the beefy CarsGuide pram into the healthy 470-litre (VDA) boot space.

Lower the 40/20/40 split-folding rear seat down and 1290 litres of volume is at your disposal. Plus there are handy bag hooks and tie-down anchors to help secure loose loads.

You can also tow a braked trailer up to 1.8 tonnes (750kg unbraked), but don’t bother looking for a spare of any description, a repair/inflator kit is your only option.

“Practicality” is about as relevant to this car as a code of ethics is to a drug dealer or a contract killer, because the SL63 buyer is hardly worried about cupholders and boot space. For what it's worth, there are four cupholders in the two-seater cabin (which might explain why owners aren't worried about their liquid carrying prospects) and a minimum boot space of 364 litres and a maximum - with roof up - of 504, which is actually not bad.

Cleverly, there's a little robot-operated luggage cover inside the deep boot that stops your gear from being crushed when the roof goes down.

There's also space in the long doors where you might secrete a bottle of wine that would get a NSW Premier fired if he thanks you for it, and a bin in the console to hide your phone.

It’s difficult to ponder the idea of value when a car is already approaching $400,000 at a rapid rate even before you start piling on the options. On the plus side, for a list price of $368,715 you do get an extremely long list of standard equipment.

The SL has always been completely unapologetic about its size.

Edited highlights include leather on almost every available surface, heated and cooled electric seats with a fan heater for your neck, a B&O stereo that will shatter the windscreen on request, aluminium trim that's real aluminium (mostly), Active Ride suspension, sat nav, dual-zone climate control, active cruise, LED headlights and a huge swag of safety gear.

The 12-speaker stereo also has DVD, limited smartphone integration via Mercedes' COMAND system, a seven-inch screen and, of course, Bluetooth.

Under the bonnet is BMW’s (B58) all-alloy 3.0-litre twin-scroll turbo intercooled, in-line six-cylinder engine, driving all four wheels via an eight-speed automatic transmission and electronically controlled clutch pack, as well as an electronic limited-slip differential at the rear.

It features high-pressure direct-injection and BMW’s ‘Valvetronic’ system managing air flow to the intake side, to produce 285kW at a relatively high 5800-6500rpm. But the big punch is 500Nm of peak torque from just 1900rpm all the way to 5000rpm.

The M440i is also a mild-hybrid with a 48-volt starter motor-generator and supplementary battery able to give an 8.0kW kick at low engine speeds.

The SL63 is powered by Mercedes’ increasingly famous V8, with two turbos along for the ride to add oomph and cut the car's famous consumption, at least slightly. The 5.5-litre unit produces a massive 430kW and a scarcely believable 900Nm of torque.

All of that heads rearward via a seven-speed dual-clutch transmission that helps sling the 4.6m, 1848kg machine to 100km/h in 4.1 seconds.

BMW’s official fuel economy figure for the M440i xDrive Gran Coupe, on the ADR 81/02 - urban, extra-urban cycle, is 8.2L/100km, the 3.0-litre turbo six-cylinder emitting 187g/km of C02 in the process.

Stop/start is standard, and we saw an average of 11.1L/100km over city, B-road and freeway running during a week with the car.

With the 59-litre tank brimmed (with minimum 95RON premium unleaded) that real-world test number translates to a range of around 530km.  

Much as is the case with the price, there's no real way to soften the blow here - the SL63 drinks like a footballer on Mad Monday, except it does it every day. The official combined cycle figure of 10.2L/100km is quite easy to double, as we did, averaging 21L/100km in mostly flowing suburban traffic. In the car’s defence, the accelerator pedal spent a good deal of time near the firewall.

The SL does have stop-start to help reduce its considerable environmental impact.

BMW says the M440i xDrive Gran Coupe will accelerate from 0-100km/h in 4.7sec, and I reckon the threshold for a properly quick car is sub-five seconds.

The 3.0-litre turbo six develops its peak power of 285kW between a relatively lofty 5800-6500rpm, but the big number is a solid 500Nm punch of pulling power delivered between 1900-5000rpm.

Squeeze the throttle pedal pretty much anywhere in the rev range and the response is glorious. Rapid acceleration accompanied by raucous engine noise and rorty exhaust note (albeit with some synthetic support). Various pops and bangs in the Sport settings add extra entertainment.. 

The eight-speed auto gets some electric support from the mild-hybrid system to fill the torque gap on up shifts, and the result is a conventional torque-converter transmission that behaves like a dual-clutch.

Shifts are seamless in general driving, and satisfyingly quick in a more aggressive mode, the wheel-mounted paddles dialing up the fun in manual changes. 

Suspension is double wishbone front and multi-link rear with the standard ‘Adaptive M Suspension’ built around an adaptive damper set-up.

The change between the ‘Comfort’ setting to the ‘Sport’ or ‘Sport+’ calibration is close to instant and makes a discernible difference, especially in terms of ride comfort.

I found the best ‘Individual Sport’ arrangement to be damping in Comfort, with the steering engine and transmission in Sport. The car flows so beautifully through corners with urgent response from the powertrain.

By all means dial up the suspension if you’re having a real crack, but the car feels superbly balanced, stable and predictable in Comfort (front to rear weight distribution is 50:50).

The electrically-assisted variable-ratio steering is nicely weighted with good road feel, and the grippy sports steering wheel is a nice point of contact.

The xDrive AWD system’s default setting is rear-biased, although it will push most of the drive forward when required. But the RWD feel is unmistakable. 

The M440i weighs in at around 1.9 tonnes but feels lighter and more nimble than that figure would typically indicate.  

A standard electronically-controlled M Sport limited-slip differential puts the power down confidently. I have a favourite LSD test corner on my regular evaluation drive, a sharply twisting and rising left-hander.

Rolling into it in a low gear before planting the throttle mid-corner, the car simply hunkers down without a hint of fuss (or traction loss) as it rockets out the other side.

Optional M Sport front seats ($2000) provide comfort and firm location in equal measure and in terms of ergonomics BMW knows how to focus on the driver and set-up an efficient environment. Key controls are perfectly positioned and simple to operate.

I have an issue with the ‘Lane Departure Warning’ function, however, which is too quick to intervene and overly intrusive when it does so. I turned the ‘Steering Intervention’ function off. You can dial down steering wheel vibration warnings, too.

The standard M Sport brakes feature big vented rotors front and rear, with fixed four-piston front calipers doing the bulk of the work. They’re strong but don’t bite or release too aggressively. It’s easy to grease in a smooth application. 

There are a number of impressive things about the way the SL drives. Firstly, astronauts will be familiar with the galactic thrust of the V8. It seems endless, seamless and ready to sling the big coupe into the outer atmosphere. Few engines of any kind can match the relentless go on offer in the SL and much of the credit should go to the seven-speed twin-clutch transmission.

When you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops.

Containing a torque figure like the twin-turbo V8's requires a lot of electro-trickery to stop you from being launched off the road. The great thing about all that stuff is that it works unobtrusively and smoothly.

Mashing the carpet in an SL without traction control would create much sound and smoke but little forward progress, such is the twist on tap. The SL has a range of modes from full-nanny (which is meant to keep you on the slippery Alpine road you've chosen to get you to some Swiss ski resort) while turning the dial all the way around to Race loosens the bonds.

It's in this mode you'll have the most fun and it does seem that the intermediate settings are a bit of a waste of time. Race mode does little to diminish the amazing ride quality provided by the active suspension setup, but relaxes the reins on the huge rear tyres. Exiting roundabouts is suddenly a huge laugh, with the tail cheerfully breaking traction and the two-mode exhaust thundering in a most pleasant way.

Better still is that when you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops, with more on the way when you lift off. There's little to match the aural pleasures of a properly tuned V8 and Mercedes has resisted the temptation to quieten it down on the outside and generate a fake noise for the inside. Although that would be stupid in a convertible, if you think about it.

The SL63, despite its AMG badge, isn't about all-out handling, of course. The Ferrari California would definitely show it how it’s done on a winding country road. The SL is more about flow, building momentum and rarely shifting down to second gear. The monstrous torque is enough to keep things rolling but should you wish for a bit more of the exhaust bellow, second is there for the taking.

Hustling the big convertible feels wrong, not because it can't do it, but because it's not really what it's for. Having said that, it offers a kind of fun that nothing else on Earth will provide, not even a Bentley GTC.

With the roof up, the SL63 is a quiet place but not remarkably so. The huge sticky tyres do the cabin's hush no favours, with an annoying roar on a wider range of surfaces than you might expect.

Roof down, it's hardly a paragon of virtue. A lot of wind noise reaches the cabin, even well below the huge speeds the SL can reach. So if you want to talk, it's windows up you'll need to deploy the mesh screen that bridges the roll hoops.

Six airbags, ABS, stability and traction controls, blind-spot sensor, lane-departure warning, brake assist, active safety bonnet, lane-keep assist, driver attention detection, AEB.

The M440i Gran Coupe is covered by BMW’s three-year/unlimited km warranty (including paintwork), as well as 12-year/unlimited km anti-corrosion (perforation) cover. 

That’s off the premium market pace now with Genesis, Jaguar, and Mercedes-Benz at five years/unlimited km and Lexus set to join them from January 1st, 2022. 

That said, roadside assistance is provided for the duration of the main warranty, but it’s worth noting “rattles and squeaks” are only covered for one year.

Service is condition-based, the car telling you when maintenance is required, and a range of service packages are available. The basic plan covering a 4 Series for five years/80,000km comes in at $1750. 

The SL63 is covered by Mercedes' three-year/unlimited kilometre warranty. And, er, that's it.