Mercedes-AMG GLC63 vs Porsche Cayenne

What's the difference?

Obviously, I had nothing to worry about. The GLC 63 S is the same boisterous, silly car I drove 18 months ago, just with a few new bits to improve the package. As ever, the GLC 63 S is all about the experience - big noise, huge grip but all in comfort with plenty of gadgets.

The only real issues are price, service pricing and the length of the warranty. The first two probably won't bother most owners and one hopes the third won't be problem, but it would be nice if the length was reflected in the price.

If you care about badge, it has impeccable credentials, the AMG stripes and that plate on the engine with the builder's name. They're good credentials. The GLC 63 S has some very determined and capable competition, but none of them blend the speed, overall comfort and sheer sensory silliness of the AMG.

Of all the super SUVs I've piloted, the Porsche Cayenne Turbo GT is the best all-rounder in terms of performance, comfort, cabin technology and style.

As a family car it's roomy, practical and easy to use and drive daily.

As a performance car the Turbo GT is stupidly quick, with the agility of a sports car. Sure, a 911 would leave it behind on a twisty race track, but this SUV is close to having that sportscar experience and keeping your family, as well.

As before, the GLC 63 S comes in wagon and couple bodystyles. Little has changed, with just the usual tweaked front and rear bumpers and mildly redesigned headlights.

All the good bits have remained, like the 'Panamericana' grille from the AMG GT monsters, the jet wing-inspired front bumper and plenty of open space to feed the radiators and intercoolers.

Neither the wagon nor coupe is a pretty machine, but no mid-size SUV is much of an oil painting, with the exception of the Jaguar F-Pace.

The 'Night Package' is still a standard inclusion, blacking out various bits and pieces and looking good when allied with the dark alloys. They both look tough, though, which is classic AMG DNA.

Inside is pretty much the same as before, with just two obvious changes. The new Alcantara-trimmed steering wheel, again from the AMG GT, and also on the C 63 S, joins the party with a more expensive look and feel.

And the new MBUX screen is wider and looks much more at home in a $165,000-plus car. It's still a bit old-feeling, but the digital dash adds a bit of techno-style while the garish speaker covers don't.

This might be a personal thing but to me nearly all Porsches look better from the back than the front.

It's the wide stance and powerful haunches, the hunkered down suction-capped-to-the-road look that does it for me and the Cayenne Turbo GT, despite being an SUV, passes this important Porsche checklist item.

The GT aero kit only serves to make this SUV look more of a beast, and the gold-bronze looking satin Neodyne wheels are a Porsche theme that I've not always been a fan of, but I get the historic connection.

If only the Turbo GT could look a little less like other Cayennes from the front. This is the king of the SUV range and despite the apron and bumper already being exclusive to this model, there should be more.

Vents in the wheel arches, carbon bonnet with nostrils GT3-style perhaps? Or is that going too far? If you do want something more lairy then there's always the Urus.

The Cayenne Turbo GT's cabin is stunning in its plushness and modern surprises such as the passenger display, the hoodless instrument digital cluster, the lashings of Race-Tex upholstery everywhere. It's perfectly Porsche. High-performance meets high-end.

It's also highly practical. Let's talk about that.

A family of four will love any GLC. The wagon's extra headroom over the coupe is useful if not life-changing, while the knee, leg and foot room are generous. Front seat passengers enjoy comfortable seating as long as you're not too keen on pudding.

Underneath, the upward sweep of the centre console is a pair of cupholders and a wireless charging Qi pad that will fit larger phones. Under the split armrest is a small but handy console bin, inside which you'll find USB-C ports.

Two more USB-C ports in the rear join a 12-volt socket and there are also climate controls for the rear seat passengers. The centre armrest pops open with a shallow, carpet-lined tray and two cupholders pop out the front. Each of the four doors has a bottle holder, too.

The boot space is unchanged for each bodystyle - 550/1600 litres for the wagon and 500/1400 litres for the coupe. Both have high loading lips, which is something to consider if you're hauling heavy things about or have trouble lifting items to a reasonable height.

The Porsche Cayenne Turbo GT only makes one compromise on practicality and that's the removal of the middle seat in the back, which, with just two kids isn't used all the time but on average we might need it once a week for school mates and cousins.

Instead of a middle seat there is a shallow tray, which will fit a phone or in our case leaves and rocks found at the park.

So, yes, the Turbo GT is a four-seater only, but this is a spacious, large SUV with good head and legroom, wide-opening doors for easy entry and exit, and air suspension which can raise and lower the height for easy access.

Storage is excellent with enormous door pockets in the front and back and there are four cupholders.

There's a wireless phone charger in the front and two USB-C ports as well, plus two USB-C sockets in the back.

Four-zone climate control means the kids in the back can set their own temperatures. They also have heated seats.

I was disappointed to see there aren't sunshades for the rear windows - pretty vital in Australia where it feels like we're only about 50 metres away from the sun.

The Turbo GT's 576-litre boot just managed to fit our pram and a week's shopping, which is our minimum standard for living. Any more space is a bonus.

The Turbo GT is the king of Cayennes, so it shouldn't surprise anybody that it's also the most expensive with its list price of $364,700.

Lamborghini's Urus lists for $409,744  and is the Cayenne Turbo GT's not-so-subtle Italian cousin, sharing the same platform and engine.

Both are in my mind the best performance SUVs on the planet. It just depends how conspicuous you want to be.

Then there's Bentley's V8 Bentayga which isn't blessed with the Porsche's good looks but would still be all over the Cayenne if the two happened to meet at a race track.

So, why is the GT Turbo the king of the Cayennes? What makes it better? For all the reasons you'd think - it's the fastest, most powerful, most luxurious and most equipped Cayenne in the range.

We'll get into mind-bending engine and performance specs soon, but first let me take you through the standard features on a car that's anything but standard.

Coming standard and exclusively to the Turbo GT are 22-inch 'GT Design' wheels in satin 'Neodyne' with full-colour Porsche centre caps, an active rear spoiler, Turbo GT front apron, dual titanium exhaust, rear apron with diffuser, 'SportDesign' side skirts, wheel arch extensions, a lightweight carbon roof and tinted LED HD-matrix headlights.

Inside, and also exclusive to this grade, is the 'GT Interior Package' with 'Race-Tex' upholstery throughout with 'Deep Sea Blue' stitching on the front seats and centre console and the armrests and dashboard.

There's also the 'Carbon Interior Package' which includes dashboard and door trim elements.

Race-Tex trim is applied to the 'GT Sports' steering wheel, roof lining and gearshift, too.

The adaptive active air suspension, which can lower the car by 15mm, is standard and only available on the Turbo GT, too.

The soft-close doors are standard (a cost option on lower grades), as are the stainless steel pedal covers.

The rest of the features are also found on lower grades and include the 12.65-inch digital instrument cluster, head-up display, proximity unlocking, 12.3-inch multimedia touchscreen with sat nav, wireless Apple CarPlay and Android Auto, digital radio, a 10-speaker Bose sound system, heated front seats, rear privacy glass and an auto tailgate.

Four-zone climate control is standard on the GT Turbo, too, and so are heated rear seats.

Our car had several options fitted such as the front passenger display ($2860) and the Deep Sea Blue Accent Package.

The passenger display is a crowd pleaser, but as a family car my kids felt like they were missing screens in the back seats, too. Well, in my day...

An AMG 4.0-litre twin-turbo V8 brings the thunder, with a massive 375kW and 700Nm of torque. That's plugged into a nine-speed MCT (multi-clutch as opposed to twin-clutch) transmission and Merc's '4Matic+' all-wheel drive system.

With all that power and grip, you'll crack the ton in a supercar-baiting 3.8 seconds. One little point to note is the engine has active mounts.

Should you fancy turning your tinny into a landspeedboat, you can tow up to 2000kg for a braked trailer, and 750kg unbraked.

As a middle-aged parent with two children, a Porsche that I don't have to crawl into and out of like a cubby house is a great thing.

What's even better is that this ‘easy access' Porsche is every bit as brutally powerful and fast as the quintessentially ‘pure' Porsche, the 911. Actually, it's more powerful and faster.

The Turbo GT's twin-turbo 4.0-litre V8 petrol engine makes 485kW and 850Nm with drive going through an eight-speed transmission to all four wheels.

In comparison, a Porsche 911 GT3 RS, arguably the most brutal and anti-social 911, has 386kW/485Nm.

I haven't made a mistake. Those are the real numbers. And it's only when you step on the accelerator in the Cayenne Turbo GT, and it feels like somebody's sat down on your chest, that you realise what a big deal this is.

That is such a colossal amount of oomph that this 2.2-tonne family SUV can accelerate from 0-100km/h in 3.3 seconds.

The 911 GT3 RS can do it in 3.2 and it has a roll cage and a fixed rear wing the size of a bedroom door.

And yes, we're now coming into a digital age where Teslas and other electric SUVs are quick, too, but can they go around corners like a Porsche Cayenne Turbo GT?

Do they have the same rumble and roar as a twin-turbo V8 that's terrifying and enticing at the same time.

The correct answer is, absolutely not.

Mercedes reckons you'll get 12.2L/100km on the combined cycle which seems laughable at first and then you see what it actually does. To be fair, the car I drove on the launch copped a hammering and was hovering around the 17.0L/100km, with the start-stop and coasting functions playing only cameo roles.

Seriously? This is a 2.0-tonne twin-turbo petrol V8 with a 90-litre fuel tank. Even the Porsche specs sheet doesn't understand the question because in the column for fuel efficiency there are three letters - tbc.

My own testing saw me record 22.5 L/100km at the fuel pump, which means I enjoyed driving the car very much.

A little digging around reveals Porsche globally claims the Turbo GT will use 12.6L/100km, over a combination of open and urban roads.

You might not have as much fun as I did but easing back a little might get you closer to the 700km of range this more frugal consumption figure appears to offer.

While efficient it isn't, I'm not going to mark the Turbo GT too much here because compared to its petrol rivals the fuel consumption is what I'd expect from such a high-output heavy SUV.

Like any V8-powered AMG, the twin-turbo engine absolutely dominates the GLC 63 S. Even at walking speeds you can feel the serious firepower on offer, just a flex of your ankle away.

The figures are colossal - 375kW (over 500 horsepower) and 700Nm pushing around two tonnes of mid-sized SUV. Its famed bark is bettered only by Jaguar's completely unhinged, and surely borderline illegal, 5.0-litre supercharged V8.

You need to know you've got plenty of tech underneath you to make this stick to the road. The 21-inch alloys are wrapped in 265/40s at the front and 295/30s at the back, Continental Cross Contacts if you're interested.

They should - and would - ruin the ride, but the standard fitment of air suspension means that in normal driving, the GLC 63 S is firm but comfortable. A BMW X3 M is much harder, especially at the rear, going without the complex and heavier air set-up.

The air suspension is probably the pivotal piece of chassis tech that makes this car so versatile. While it's got driving modes up the wazoo - including the new 'Slippery' mode - it's a perfectly agreeable daily driver.

Leave it in comfort, accept that it has a firm ride and you're in good shape for the school run or the commute. You just sail along on a light throttle because there is virtually no turbo lag.

Whack it in Race and you can attack your favourite empty, bendy road with all the grip you could ever need.

The steering is remarkably light and direct for such a chunker and the optional carbon ceramic brakes were never bothered by what I could throw at them.

The V8 roars and spits and crackles, the gearbox shifting seamlessly up and down through the ratios. It's blissfully silly.

In a way, it's a velvet fist in an iron glove - comfortable inside but happy to headbutt the horizon with little provocation.

I'd prefer it if the transmission was a bit more decisive on slow speed shifts and you'll have to prepare yourself for a lot of wearying road noise on long trips. The latter is the price you pay for a ton of grip.

Never have I met a car this powerful and superbly athletic that is as pleasurable to drive alone on great, fast roads as it is to pilot at 50km/h in the suburbs with a family on board.

It exceeds my understanding of engineering that something this large can move so quickly. That in an instant can turn and tip into a corner with such precision and effortlessness.

Yet it can switch seamlessly and happily to coping with speed bumps and potholes, delivering a ride so comfortable it'll send babies off to sleep. And it did.

The only issue, and this is such a tiny thing, is the dash-mounted gearshift, which means having to reach up and select Drive or Reverse or Park, which, when executing a three-point turn, is necessarily frustrating.

Still, I'm giving the Turbo GT a 10 out of 10 for driving under all conditions, and we didn't even go off-road, which of course you can do, as long as it's not too wild.

The Porsche Cayenne Turbo GT hasn't been locally crash tested and so doesn't have an ANCAP rating.

That's quite normal for super high-end cars. But, when this third-generation model first arrived in 2017 it was tested by ANCAP's European equivalent, Euro NCAP, and was awarded the maximum five stars.

There's AEB which operates at city, urban and highway speeds, and lane keeping assistance, and lane change assistance which is a form of blind-spot warning, and adaptive cruise control. You can option rear cross-traffic alert, as well.

A space saver spare wheel is under the boot floor.

Mercedes Benz offers a three year/unlimited kilometre warranty with roadside assist which is not really up to scratch for a premium brand. Yes, the cars are complex but they're also expensive, so the investment should come with a commensurate warranty.

Service intervals are generous at 12 months/20,000km (as opposed to the 25,000km of other GLCs) and the capped price servicing means you'll know what you're paying.

Mercedes offers you the choice of an up-front payment or pay-as-you-go. Upfront ranges from $4050 for three services, $6100 for four, and $6850 for five.

If you go with PAYG, three services is a hefty $5000. Basically, each service is at least a grand when averaged out over time and that's pricey.

Service inclusions differ between your chosen method, but only slightly. The pricing includes filters, oil and, unusually, spark plugs and brake fluid, but that's small comfort.

The Cayenne Turbo GT is covered by Porsche's three-year, unlimited kilometre warranty, which is lagging behind in terms of duration even compared to other luxury brands such as Mercedes-Benz, which offers five years.

Servicing is recommended annually or every 15,000km, although there isn't a capped price maintenance plan with final costs determined at the dealer level (in line with variable labour rates by state or territory).