Mercedes-Benz GLS-Class vs Audi RS Q8

What's the difference?

The GLS63 is an intimidating beast from afar, but it rewards its occupants in almost every way. Yep, there really isn’t a box it doesn’t tick without serious compromise, such is its breadth of capability.

If there was ever a Swiss Army Knife of cars, the GLS63 is definitely a contender for the title, one that makes it very hard to wipe the smile off your face. Just make sure you can fit it in your garage first…

The Audi RS Q8 is every bit as competent as it is striking to look at - and it’s plenty striking to look at. It surely won’t appeal to everyone, but if you’re in the market for a big, boisterous SUV, the Audi ticks plenty of boxes. 

And if you happen to be in the market for a Lamborghini Urus, be sure to drive this before signing on the dotted line...

If the GLS63 was a Marvel superhero, it would undoubtedly be the Hulk. Simply put, it has road presence like few others. In fact, it’s frankly menacing.

Of course, the GLS is already pretty intimidating due to its sheer size and blocky design, but the GLS63’s full-fat AMG treatment takes it to another level.

Naturally, the GLS63 gets an aggressive body kit, with its purposeful bumpers, side skirts and rear spoiler serving as instant reminders of what you’re dealing with, but it’s AMG’s signature Panamericana grille insert that really hammers home the point.

Around the side, the GLS63’s 22-inch alloy wheels with staggered tyres (front: 275/50, rear: 315/45) make their presence known, positioned below the wheelarch extensions.

That said, some fun’s also had at the rear end, where the GLS63’s diffuser element integrates the foreboding sports exhaust system with quad tailpipes very neatly.

The focused Multibeam LED headlights also look the part, while the opposing LED tail-lights tie everything together outside quite nicely.

Inside, the GLS63 stands out from the GLS crowd with its sports steering wheel with Dinamica microfibre accents, and multi-contour front seats, which are covered in Nappa leather alongside the armrests, dashboard and door shoulders and inserts.

Of note, the doors bins are unfortunately of the hard plastic variety, which is very disappointing in a vehicle that costs this much. You would expect that cow hide would also been applied to them, but alas it isn’t.

The GLS63’s black headliner serves as an obligatory reminder of its sporting intent, and while it makes for a dark cabin, metallic accents are prominent throughout, while the optional trim (our test vehicle had carbon-fibre) mixes things up, alongside the ambient lighting.

And let’s not forget the GLS63 is still loaded with plenty of cutting-edge technology, including a pair of 12.3-inch displays, with one the central touchscreen and the other the digital instrument cluster.

Both are powered by Mercedes’ class-leading MBUX multimedia system and feature Apple CarPlay and Android Auto support. This set-up arguably remains the best there is today thanks to its speed and breadth of functionality and input methods.

It looks plenty striking, the RS Q8, especially dressed in the bright green paint work of that harks to its Lamborghini sibling.

There are the massive black-on silver alloys, the bright red brake calipers the size of dinner plates, and the body creases that bulge out over the rear arches like a 1950s’ pin-up model. All of which looks great.

Step around to the rear of the vehicle and you’re greeted with twin exhaust exits bookending a massive textured diffuser, a single light LED that splits the multi-globe LEDS, and the slick roof spoiler.

It’s the front-on view, though, that’s the most imposing, with a black meshed grille that looks as big as a hatchback, two LED-filled slimline headlights and massive side venting.

Climb into the cabin and you’re met by a wall of leather and technology, not to mention a sense of immense space.

Everything is digital and touch activated, of course, and yet it doesn’t feel garish and overdone.

Measuring 5243mm, 2030mm wide and 1782mm tall with a 3135mm wheelbase, the GLS63 is an upper-large SUV in every sense of the term, which means it’s also very practical.

For example, cargo capacity below the load cover is decent, at 355L, but stow the 50/50 power-split-folding third row via the boot and it’s very good, at 890L, or drop the 40/20/40 power-split-folding middle bench, too, and it becomes a cavernous 2400L.

Better yet, the boot’s aperture is almost square, and its floor’s flat, while there’s no load lip to contend with, making loading bulkier items even easier. Up to four tie-down points are also on hand (depending on seating configuration) to secure loose cargo.

Under the false floor is the space-saver spare, which is to be expected, but what isn’t expected necessarily is the fact there’s also enough room there for the cargo cover when it’s not in use, which would be the case if six or more passengers are regularly onboard.

Moving into the power-sliding second row, the GLS63’s practicality is once again brought to the fore, with up to six-plus inches of legroom available behind my 184cm driving position.

There’s also two inches of headroom with the panoramic sunroof in situ, not to mention just enough toe-room. The GLS63’s small transmission tunnel and sheer width also mean three adults can be seated on the middle bench with few complaints.

Amenities-wise, the second row has map pockets on the front-seat backrest and a small fold-down cubby below the rear climate controls, with it containing two slots for smartphones and a pair of strategically placed USB-C ports.

The rear door bins can take one large bottle each, while a fold-down central armrest is also on hand, featuring a shallow tray and retractable (and flimsy) cupholders.

Alternatively, the $2800 Rear Seat Comfort Package fitted to our test vehicle subs in a tablet that can control the multimedia system, a wireless smartphone charger and a small cubby into the former, as well as a heated/cooled cupholder atop the rear of the centre console.

In the third row, it’s not quite as roomy if you’re an adult. With the middle bench in its most accommodating position, my knees still brush up against its backrest, which is to be expected given it’s primarily designed for children. I also have an inch of headroom there.

Nonetheless, getting in and out of the third row is relatively easy as the power-operated middle bench tumbles forward and provides just enough space to make entry and exit somewhat graceful.

When seated, rear occupants are treated to two USB-C ports and one small cupholder each, so they’re arguably taken better care of than those in the middle.

Child seats are well and truly accommodated, with four ISOFIX and five top-tether anchorage points fitted across the second and third rows, although the latter will inevitably prove to be a much tighter fit.

The driver and front passenger are still taken care of, with a front cubby taken up by two heated/cooled cupholders, a wireless smartphone charger, two USB-C ports and a 12V power outlet, while their door bins take one large and one small bottle each.

In-cabin storage options include the large central storage bin, which hides another USB-C port, while the glovebox is on the smaller side, with about a third of it taken up by the fragrance, which is pumped into the cabin to ensure the interior always smells its best.

Very damn practical, actually. Which is no great surprise, given the size of the thing, but still impressive when you consider the performance it can conjure. 

It stretches more than 5.0m in length, and those dimensions translate to an absolutely massive cabin, which is actually most noticeable in the backseat, which is gigantic. You can essentially park an Audi A1 back there, such is the space on offer, but you’ll also find two USB ports, a 12-volt power outlet, digital air-con controls and leather as far as the eye can see.

There are two cupholders up front, another two in the pull down divider in the rear, and bottle holders in all doors, as well as ISOFIX attachment points for child seats. 

Storage? Well, there’s lots… The backseat slides forwards or backwards to prioritise space for either passengers or cargo, unlocking 605 litres of luggage room, but with them folded flat, the RS Q8 will deliver 1755L of space. Which is a lot.

It feels a little strange marking such an expensive SUV so highly for value, but the truth is that, comparatively at least, it’s something of a bargain.

As I mentioned above, the key competitor for a car like this is the Lamborghini Urus (which is Audi’s stablemate) and that will set you back close to $400k. The Audi RS Q8? Almost half that, at just $208,500.

See, it’s a steal! For that money you get an engine that could power a small city and the kind of performance kit required to make a 2.2-tonne SUV go around corners at speed. But we’ll come back to all that in a moment.

You also get massive 23-inch alloys wheels outside, with red brake calipers peeking out from behind, as well as RS adaptive air suspension, a qauttro sport differential, all-wheel steering, electronic active roll stabilisation, Matrix LED headlights, a panoramic sunroof, and an RS sport exhaust. 

Inside, you’ll find 'Valcona' leather seats that are heated in both rows, ambient interior lighting, leather everything, automatic sun blinds, illuminated door sills and just about every other piece of kit Audi has in its sizeable grab bag.

On the tech front, you’ll find 'Audi Connect plus' and Audi’s 'Virtual Cockpit', and a 17-speaker Bang and Olufsen 3D sound system that pairs with twin (10.1-inch and 8.6-inch) screens, capping off a seriously tech-heavy cabin. 

The GLS63 is powered by a familiar 4.0-litre twin-turbo V8 petrol engine, with its version producing a thumping 450kW of power at 5750rpm and 850Nm of torque from 2250-5000rpm.

This unit is mated to a nine-speed torque-converter automatic transmission and AMG’s fully variable 4Matic+ all-wheel-drive system with torque vectoring and a rear limited-slip differential.

This set-up also features Mercedes’ EQ Boost 48V mild-hybrid system, which actually gives a 16kW/250Nm electric boost in short bursts, such as when accelerating off the line.

Speaking of which, the GLS63 sprints from a standstill to 100km/h in just 4.2 seconds, while its top speed is electronically limited to 250km/h.
 

The Audi RS Q8’s 4.0-litre twin-turbo V8 produces a monstrous 441kW and 800Nm, sent to all four wheels via an eight-speed triptronic automatic.

At more than two tonnes, it’s a lot of car, but that’s also a lot of power, and so the go-fast SUV can produce a cracking sprint to 100km/h of just 3.8 seconds. 

The RS Q8 is also equipped with a 48-volt mild hybrid system that is ostensibly designed to lower fuel use, but is actually more useful at plugging any turbo holes when you really plant your foot.

The GLS63’s fuel consumption on the combined-cycle test (ADR 81/02) is 13.0L per 100km, while its carbon dioxide emissions are 296 grams per km. All things considered, both claims are unsurprisingly high.

In our real-world testing, we averaged a fearsome 18.5L/100km over 65km of driving, split between highways and country roads, so not your usual mix. A very heavy right foot definitely influenced that result, but don’t expect to do too much better in a normal run.

For reference, the GLS63’s 90L fuel tank can be filled up with 98RON petrol at a minimum.

For every action there is an equal and opposite reaction, right? Well the reaction to all that power is a whole lot of fuel use. 

Audi reckons the RS Q8 will sip 12.1L per 100km on the combined cycle, but we suspect that’s wishful thinking. It will also reportedly emit between around 276g/km of C02.

The big SUV is fitted with a huge 85-litre tank.

Frankly, the GLS63 has absolutely no right being as capable as it is. It’s a really big bus that’s legitimately convinced it’s a sports car half its size.

Being a GLS variant, the GLS63 has independent suspension consisting of four-link front and multi-link rear axles with air springs and adaptive dampers, but its party trick is the addition of active anti-roll bars.

In what feels like magic, the GLS63 is simply not intimidated by corners, despite having massive dimensions and a considerable 2555kg (kerb weight) to deal with.

The active anti-roll bars make the GLS63 so much easier to drive fast through the twisty stuff, almost eliminating body roll, taking one key variable out of the equation for the driver. Active engine mounts are also fitted, helping to settle things even further.

The electric power steering on hand is also good. It is speed-sensitive and has a variable ratio, which basically makes the set-up more direct when it needs to be. It’s typically light in hand, too, until one of the sportier drive modes is engaged and extra heft is added.

So, handling is scarcely believable, which means the ride must be compromised, right? Yes and no. With the adaptive dampers in their softest setting, the GLS63 is very compliant. In fact, we’d say it feels luxurious when compared to other high-performance SUVs.

That said, our test vehicle was fitted with the optional 23-inch alloy wheels ($3900), which look the part but expose sharp edges and other road imperfections, not to mention generate noise easily heard inside. Naturally, feedback is exacerbated in the sportier drive modes.

Anyway, there’s more performance, and the GLS63 has the rest in spades. Its engine is a powerhouse in every sense of the word. It’s so powerful, in fact, that it hilariously hunkers down off the line or when suddenly accelerating at low speed.

Thanks to the mild-hybrid system, wads of torque is available from the get-go, making for a highly responsive driving experience, even in those rare moments when the engine isn’t on song.

While not as characterful as some of the other members in the 63 series, the GLS63 still makes some thoroughly entertaining noises, with its sports exhaust system popping like mad while on the overrun.

All of this ability is very well and good, but you need to be able to pull up quickly, and the high-performance braking package (400mm front and 370mm rear discs with six-piston fixed callipers and single-pot floating stoppers respectively) mercifully does exactly that.

How do you describe the drive experience of the RS Q8? Utterly, utterly surprising.

I’ll give you an example. You approach the hulking SUV, check out its massive alloys wrapped in performance rubber, and you know - just know - that it will ride like a broken billycart on anything but the most silky smooth of road surfaces. 

And yet, it doesn’t. Aided by its clever air suspension (which drops the ride height by 90mm when switching between Off-Road and Dynamic modes), the RS Q8 positively glides ever dodgy road surfaces, stifling lumps and bumps with surprising aplomb. 

So then you think, ok, we’re set up for compliance, so this big behemoth will go around corners with all the dynamism of a spilled bowl of cereal. 

But again, it doesn’t. In fact, the Audi RS Q8 attacks corners with incredible stiffness, the active anti-roll systems weaving their dark magic to keep the towering SUV straight and true, and with barely a hint of body roll.

The grip is ferocious (we’re yet to find its outer limits) and even the steering feels more direct and communicative than in other smaller, ostensibly sportier Audis. 

The result is a tech-heavy spaceship that’s surprisingly easy at slow speeds, and quiet too, even over rough roads. But one that can also activate warp speed at will, leaving smaller cars in its considerable wake on the right stretch of road. 

Downsides? It’s not quite willing to pounce off the line. Sure, it makes up for it in the long haul, but there is a noticeable moment of hesitation, almost as though it’s contemplating its considerably weight, before it finally lunges forward. 

It’s also so competent, so efficient, that it can leave you feeling a little detached from behind the wheel, or like the Audi is doing the heavy lifting for you. 

The RS Q8 gets six airbags, as well as a host of high-tech safety equipment, with Audi pretty much throwing everything its got at its new performance flagship.

Think adaptive cruise with stop and go, lane guidance assistance, active lane assist, blind-spot monitoring and a 360-degree parking camera. You also get a parking system, pre-sense rear for nose-to-tail collisions, and an AEB system that works at up to 85km/h for pedestrians and 250km/h for vehicles.

There’s also collies avoidance assist, rear cross-traffic alert, intersection crossing assist, and an exit warning system. 

Don’t expect Audi to crash an RS Q8 anytime soon, but the regular Q8 recorded a full five stars when ANCAP tested in 2019.

As with all Mercedes-AMG models, the GLS63 comes with a five-year/unlimited-kilometre warranty, which currently sets the standard for the premium market. It also comes with five years of roadside assistance.

The GLS63’s service intervals are relatively long, at every 12 months or 20,000km (whichever comes first). Better yet, it’s available with a five-year/100,000km capped-price servicing plan, but it costs $4450.

All Audi’s are covered by a three year, unlimited kilometre warranty, and require annual servicing. Audi will allow you to prepay the first five years of service costs for $4060.