Mercedes-Benz AMG GT vs BMW 6 Series

What's the difference?

This is no Lotus, but damn if it ain't a hell of a good time, and proof positive that electrification can enhance the V8 experience, rather than ruin it.

This isn't a car for everyone's tastes, but if you fit in to the buyer group that just doesn't really know what they want in a luxury car, it could be the perfect fit for your family. The 6 Series GT is a practical large prestige car, albeit one that will likely find very few buyers.

It's a mean, but somehow still sleek, looking beast, this big AMG, but it's also immediately recognisable as a thing of intent.

Up front, there's the huge vertical-slat grille that looks like it drove straight out of a Stephen King novel, a massively domed bonnet, and these vacuum-like side intakes that look like they could suck in stray animals.

Then, at the back, there are twin dual-pipe exits (for four in total), and an automatic wing that pops out of the rear bodywork. And all of that's capped off with these massive 21-inch forged alloy wheels hiding golden ceramic-composite brakes.

Mean, yes, but not quite as aggressive as you might expect the most powerful AMG to date to come across, perhaps.

Inside, it's more subdued again, with the AMG presenting a pretty passenger-friendly space, with all the Benz tech you'd imagine, including the massive screens, and — thanks to its air suspension and drive modes — the ability to tailor the ride to your liking, meaning a comfortable and premium experience, despite the power under your right foot.

There is no denying the 6 Series GT looks better than the old 5 Series GT. It isn't as frumpy, it looks more sporty, and to me it appears to have grown into its identity with more conviction than its predecessor.

That said, I don't necessarily like the look very much - it's a bit like a BMW X6 that has been rounded off a little and lowered down substantially. But I can appreciate some of the finer design aesthetics that it offers up: the frameless windows are a nice touch, and the swooping roofline looks smoother than a duck's back.

Other things like the active grille shutters and the air breathers ahead of the front doors are nice functional touches, and to my eye it lives up to BMW's hope of it looking "smooth but muscular". You can get the 630i with either the M Sport package, like you see here, or the more sedate Luxury Line, which is, well, more luxurious looking.

The M Sport styling and equipment package you see in the images here - with M aero kit and 19-inch wheels (ours had been upgraded to optional 20s) - help out with the athletic look of this very big vehicle.

It's huge in fact. The length of the 630i is 5091mm long, it measures 1902mm wide and sits at 1538mm tall, with a lengthy 3070mm wheelbase.

All that equates to a lot of room in the cabin, and what a sumptuous and delightful place it is to be - leather, wood and plush finishes abound.

It's not overly practical, given its size, with AMG locking in a four-seat configuration with a fixed rear pew that limits boot space. You can get folding seats, but only as part of an option package.

What you're left with is a vehicle that stretches 5054mm in length, 1953mm in width and 1447mm in height, but that serves up rear seating for only two – albeit very comfortably – and, because of the electric battery and motor being housed at the rear, boot space of just 335 litres.

There is triple-zone climate control, and the rear seating is lounge-like and luxurious, while the up-front space is ample for two full-size riders, too.

There's no spare, with AMG's 'Tirefit' puncture repair system on board.

Now, I said before that this is a bit like an X6, but it has heaps better interior space than that SUV.

As soon as you slide into the driver's seat, you feel like your inside a large car. The cabin space is plentiful, and there's an abundance of storage on offer, too: there's a split-lid armrest between the seats, a pair of cupholders, a phone storage nook with wireless charging, and big door pockets with bottle holsters.

In the back you have access to door pockets, a flip-down armrest with cupholders (that middle part of the seat can fold down completely to allow storage of longer items), and there's excellent room on offer. How many seats in the BMW 6 Series GT? Five - like, five full-size seats.

Because the roofline doesn't rake as sharply as a four-door 'coupe', headroom is excellent for adults (even of the 183cm variety, like myself), and legroom and toe room are equally very good. This is bigger in the back than a 5 Series, but maybe not as plush as a 7 Series… so I guess it makes sense numerically for its nomenclature.

Of course you get climate control in the front (and in the rear if you option it), and the materials are excellent. The media screen is tablet-style, proudly displaying 10.25 inches of high-def real estate that is both touch-capacitive and controllable by way of the central rotary controller with touchpad. And get this - you can even use gestures to control certain elements like volume, swiping and changing tracks… but you have to option that.

The fully digital instrument display is bordered by a set of incomplete dial rings, which is just odd. BMW, back yourself - your buyers can handle just having a digital screen in front of them, particularly when it's as good as this one.

This grandiose hatchback's boot is commodious - with the back seats in place it has a huge 610 litres of cargo capacity, which extends to 1800L with the 40/20/40 seats folded down using the quick release levers in the boot area.

There is no spare wheel (the BMW range is fitted with run-flat tyres) but it does have a secondary hidden storage area under the boot floor for hiding items or stowing wet gear, bathers/swimmers or muddy clothes.

For context, the X6 has 580L seats up, 1525L seats down.

The BMW 6 Series Gran Turismo range starts off with the model tested here, the 630i. It has a list price of $123,500 before on-road costs - and that's whether you buy the M Sport Line or the Luxury Line.

That's quite a lot of money. And while it has a lot of equipment to help justify the cost, the smarter dollars will probably find their way to a more affordable 5 Series.

Standard gear in this spec includes adaptive air suspension with multiple drive modes, a colour head-up display, semi-autonomous parking, adaptive cruise control with steering assistance, auto high-beam LED headlights with LED daytime running lights, DAB+ digital radio, a 16-speaker harman/kardon sound system, a 12.3-inch driver information screen and a 10.25-inch media display with sat nav, Bluetooth and 'BMW ConnectedDrive' online services.

Hey, you even get a panoramic sunroof as standard! Plus there are things like an active rear spoiler, two USB ports and four 12-volt outlets, leather trim, heated front electric seats, electric steering wheel adjustment, keyless entry, push-button start, and an automatic boot.

It also comes loaded with active safety assistance functions - we'll get to that in the safety section below.

Things it's missing at this price point? Well, heated seats are an option, but bundled nicely into the 'Comfort Package' ($3000) which was fitted to our car. The pack includes heated seats front and rear, quad-zone climate control, electric sunblinds for the rear side windows, and electric seat back adjustment. Oh, and BMW continues to gouge consumers $623 for Apple CarPlay (which seemingly didn't work in our car).

The only other 6 Series GT model available is the 640i xDrive, which is again available with the choice of M Sport or Luxury body styling. It's also pretty exxy, with a list price of $148,900, but gets a more performance-focused drivetrain, as well as extra equipment: essentially the Comfort package, plus vented front seats, interior fragrance (eight options), memory settings for the front seats, 20-inch wheels and metallic paint.

Plus the 640i has Sport+ settings - it's probably the wrong car for those - and 'Integral Active Steering' to couple with the all-wheel drive system.

It's not just what's under the bonnet, but what's at the rear axle, too.

But let's start at the front, shall we? Here, a familiar twin-turbo V8 engine lurks, producing a potent 470kW and 900Nm, which is fed through a nine-speed automatic, complete with paddle shifters and several drive modes, including the traction-limiting 'Race'.

But that is then joined at the rear by an electric motor with its own two-speed transmission, and which produces 70kW and 320Nm – or up to 150kW for 10-second blasts under heavy acceleration.

Combine both, and you're tapping into around 620kW and in excess of 1000Nm, enabling a sprint to 100km/h in just 2.9 seconds, and a flying top speed of 316km/h.

Under the bonnet of the 630i is a 2.0-litre four-cylinder turbocharged petrol engine, which produces 190kW of power (at 6500rpm) and 400Nm of torque (from 1550-4400rpm). It uses an eight-speed automatic transmission, and is rear-wheel drive.

That may not seem a lot considering the size of this machine, but consider that some of the steamiest four-cylinder hot hatches have nearly the same outputs, and you realise this engine offers up a far-from slouched approach to propulsion.

The 640i xDrive has a 3.0-litre six-cylinder turbocharged engine with 250kW of power and 450Nm of torque. It gets the same eight-speed auto, but as the xDrive naming indicates, it's all-wheel drive.

But this is the one you'd prefer if you want to hit highway speed in a hurry - the 0-100km/h claim is 5.3 seconds, where the 630i takes a full second longer (6.3sec) according to the company.

Fuel efficiency is surprisingly impressive for a vehicle this big and powerful, with Mercedes claiming 7.7L/100km and 175g/km of CO2 on the combined cycle.

Helping that is a the 6.1kW battery, which delivers just 12km in all-electric driving range, but helps reduce overall fuel use.

This AMG is AC power only, meaning you can't recharge using fast chargers, but the brand says its secret trick is its ability to recharge itself using captured kinetic energy incredibly quickly – largely negating the need to plug in unless you want to unlock that EV range – with Merc suggesting that, on a race track for example, the battery will discharge and charge itself continuously as you're lapping.

BMW claims fuel use of 7.0 litres per 100 kilometres, and you'll need to use 95RON premium unleaded when you fill up.

On my trip with the car, I saw about 9.0L/100km across mostly high-speed driving - some freeway, some highway, some country back road touring, and quite a bit of corners and city stuff thrown in as well. I think that's pretty respectable.

What wasn't so great was the lack of premium fuel in some of the 'away from civilisation' places on my route home. Keep that in mind if planning your own GT long-distance cruise.

There's a lot of big numbers surrounding the Mercedes-AMG GT63S E Performance, but let me throw another one at you – 245km/h.

That was the high score I saw pop up on its digital speedo as the big and electrified Mercedes flew down the main straight at Sydney Motorsport Park (formerly Eastern Creek), before my courage ran out and my foot found the brake.

That kind of velocity is mind-bending in a vehicle this big, and so is the way that power is delivered, with the AMG's big brain deciding how and when to maximise power from the engine and electric motor to deliver a constant surge of torque that shoves you back, and the GT63S E Performance into the future.

But big acceleration is hardly surprising with that much power. What is a little more impressive is how easy this four-door supercar is to wrestle around a racetrack.

Sure, the feeling-out process is a little more involved, as you figure out how and when you'll feel the weight shifting, and as your brain struggles to compute how what's happening is even possible, but after a couple of laps the AMG settles into an easy, flowing rhythm that, while never feeling light on its feet, also doesn't feels like you're piloting a bus.

At least part of that is down to the wizardry on board, like the 'AMG Air Suspension', the rear-axle steering and the limited-slip diff, all of which combine to make the GT63S feel tighter and sharper than it would otherwise.

But it's also partly down to the prodigious power on offer – perfect corner entry and exits are less relevant when you have a cruise missile strapped to your right foot that doesn't just quickly make up for any driver errors, but shrinks the space between corners to the blink of an eye.

Yes, it's heavy, and there isn't much that's pure about the go-fast experience, but it left an ear-to-ear grin on my face, and isn't that priority one for any new AMG?

How does it drive on the road? That I don't know, as this was a track-only drive day. But we will get one on a proper test soon and let you know.

I'll put this out there - if you like to drive, there are BMW models for less than this one that will put a much bigger smile on your face. Like, a 440i Gran Coupe, or even just a 330i sedan…

But if you're in BMW's target market - that being older executive buyers who want space and luxury as a priority over thrills at the wheel, you could do a lot worse.

That's because the 6 Series GT lopes along the highway without fuss - the engine easily coping with the demands of overtaking moves, the adjustable drive modes allowing a light steering and wafting suspension feel to wile away the kilometres.

There are 'Comfort' and 'Comfort Plus' modes, but the latter is a bit too spongy and can be boaty feeling. The Comfort setting is made for the highway.

It is actually pretty agile for its dimensions.

If you decide to deviate from the straight sections, you'll be able to explore a little bit of dynamic range, especially when you dial up the 'Sport' mode, which changes the damper settings, steering weight, throttle and transmission response, and even the digital dials in front of the driver to a more aggressive look.

Our car had the 'Integral Active Steering' setting, which is a variable ratio steering system that includes rear steering - that essentially helps make is more turnable in corners at highway speed, and easier to park at lower speeds. It's difficult to say whether the assistance is excellent or not short of driving a car without the tech, but to this tester it was hard to hide the size and weight (1835kg kerb weight) of the vehicle.

That isn't to say it's clumsy or lumbering - it is actually pretty agile for its dimensions, though it makes a lot more sense on long drives and coastal cruises than it does in the narrow and twisty alpine roads of the Snowy Mountains Highway that I tested it on.

There's good grip from the tyres, and strong response from the powertrain - but if it were my money, and I had to have a 6 Series for whatever reason, I'd be looking towards the 640i model, which has a thumping six-cylinder with 250kW/450Nm - certainly an engine that would be more at home in this car. Plus that model comes with AWD.

The BMW 6 Series GT range has a five-star Euro NCAP crash test score based on 2017 testing, but it hasn't been scored by ANCAP.

There's the usual array of airbags - dual front, front side, full-length curtain and driver's knee airbags are included, plus parking sensors all around, and heaps of safety tech including the 'Driving Assistant Plus' package with lane departure warning and lane keeping assist, forward collision warning, auto emergency braking (AEB) front and rear, blind-spot monitoring and rear cross-traffic alert, and adaptive cruise control with stop and go.

That's all great stuff, and so is the 360-degree camera system with adaptive display - so, if you're reversing and you turn the wheel to one side, the image on screen will move, too. It'll also go between a birds-eye view and a backing-up perspective, and that can take some getting used to.

What was less convincing in terms of the user experience was the rear auto braking, which seemed to be scared of the car's own shadow. On multiple occasions the car jammed on the brakes when reversing out of driveways on to empty streets - be it in the normal height, or the raised height setting.

The 6 Series GT has dual ISOFIX anchor points and three top-tether points are there and ready for baby seats or child seats.

The GT63S E Performance is covered by Mercedes' five-year, unlimited-kilometre warranty, and you can pre-pay your service costs to keep the prices down.

Service pricing for the electrified model is yet to be confirmed.

BMW runs a condition-based servicing plan, which means the car will tell you when it needs servicing. But you can rest assured it won't (theoretically) cost you much, with the brand's 'Service Inclusive' pack. It covers you for basic maintenance as and when required for five years/80,000km. According to BMW, that includes "annual vehicle checks, oil changes, all filters, spark plugs and labour costs for the duration of the package".

BMW offers a three-year/unlimited kilometre warranty plan, and you get the same cover for roadside assistance.