Mercedes-Benz G-Class vs Porsche Cayenne

What's the difference?

The Mercedes-AMG G 63 isn't for shrinking violets. It's bold, fast, and loud, and in second-generation form massively improved dynamically and technically. It's a lot of money, but there's a lot to love, and here's hoping it stays around for decades to come.

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.

The original (W460) G-Glass, then known as the G-Wagen (or Geländewagen for cross-country vehicle), was launched in 1979 as an ultra-capable off-roader, soon favoured by armies the world over. Arriving here in 1982, its distinctive, slab-sided form remained unchanged over the best part of four decades.

At close to 4.8m nose-to-tail, more than 1.8m across, and a bit over 1.9m tall, the G 63 is now longer (+110mm), wider (+106mm), and fractionally lower overall (-13mm), but still pulls off a convincing impersonation of a bread box.

Merc-AMG confidently quotes a drag coefficient (Cd) of 0.55 for the G 63, which isn't as bad as a brick (around 2.0… I Googled it) although it is in the same league as a heavy truck.

But it's the car's unique, upright stance, complete with pumped wheelarches and old-school flat glass, that sets it apart and draws people in. Looking more like a take-no-prisoners, functional device than a luxury cruiser, I can assure you it attracts as many admiring looks and comments as a low-flying supercar wedge.

The new-gen G 63 features AMG's vertically slatted 'Panamericana' grille, and our test example was fitted with the optional 'Night Package' ($5900) adding a range of dark exterior details including tinted indicator lenses, dark tinted glass, black exterior mirror shells and spare wheel ring, other black trim pieces and painted areas, as well as 22-inch AMG forged alloy rims.

Also worth noting, Merc has retained the G-Class's solid metal door handles, complete with the mechanism's unmistakable 'click-clack' opening and closing sound. Nice touch.

Inside, the biggest change is the upgrade from a conventional dual-gauge instrument cluster and central media stack to a pair of 12.3-inch digital screens, forming a sleek widescreen display, and bringing the G 63 in line with other recent Merc offerings.

Similarly, the gearshift moves from a traditional console-mounted set-up to Merc's 'Direct Select' lever on the steering column (exactly where the indicator stalk is located in 90 per cent of right-hand drive cars).  And the standard flat-bottom, leather-trimmed 'AMG Performance' steering wheel is a racy addition.

Like the exterior door handles, another tip of the hat to the car's heritage is retention of the horizontal grab handle ahead of the front passenger on the dash above the glove box. Nice to have something to hold on to if the going gets rough.

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.

The G-Class has never been a particularly squeezy proposition for passengers or cargo, but an extra 40mm in the wheelbase adds even more breathing space.

Getting in is the first step, and it's a big one. At 183cm tall, in an athletic mood, I could grab the A-pillar and swing up into the driver's seat in one vaguely respectable movement.

But, those side steps aren't just for show, and at the end of a long day provide a handy staging camp between terra firma and the lofty pilot's chair.

Once on-board there's plenty of room up front, with adequate storage including a bin between the seats (now with a double door opening rather than a single hinged lid), a modest glove box, oddments space and two cupholders in the centre console, and bins with space for bottles in the doors.

There's a 12-volt power outlet in the front, second row and cargo area, while there are two USB ports in the centre console bin and a charging USB port in the second row.

In the back I could have donned a dusty Akubra and still had headroom to spare, with generous foot room, and a substantial gap between my knees and the driver's seat (set to my position).

A fold-down armrest incorporates a pair of cupholders (as well as a through-port to the cargo space for long items) and there are map pockets on the front seat backs as well as space for bottles in the doors. Two adjustable air vents in the rear of the front centre console, and another pair in the B-pillars also provide climate-controlled air to those in the rear.

With the rear seats upright boot volume is quoted at 454 litres (VDA); enough to easily swallow our three-piece hard suitcase set (35, 68 and 105 litres) or the CarsGuide pram, or a largest-suitcase-and-pram combo.

There are tie-down shackles in each corner of the floor, usefully bright lighting, a netted storage area on the passenger side (containing five fluorescent emergency vests), and folding the 60/40 split rear seat liberates even more space.

Unfortunately, gaining access to that load space is fraught with compromise. First, the single-piece rear door hinges vertically and opens from right to left. No problem when you've nosed into a shopping centre space, but not so great when you're parking nose-to-tail on the left-hand side of the road.

That means you typically have a small space between you and the car behind to get the door open, and when it is at 90 degrees, you're blocked from unloading things onto the footpath until you've shut the door.

As well as that, the door has a full-size spare (alloy) wheel and tyre attached to it. Good because a full-size spare is welcome, and bad because it makes the already bulky door even heavier.

Those keen on towing things will be pleased to hear the G 63 is rated to haul up to 3.5 tonnes of braked trailer and 750kg unbraked.

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...

The G 63's 4.0-litre (M177) all-alloy V8 is closed deck design using direct-injection and a pair of twin-scroll turbos to produce 430kW at 6000rpm and no less than 850Nm from 2500-3500rpm. That's 10kW/90Nm more than the 5.5-litre twin-turbo V8 it replaces!

To improve throttle response and optimise efficiency, the turbos are located inside the engine's 'V', improving air flow and shortening the distance from the exhaust side to the turbos, and in turn, from the turbos to the inlet side.

And the housings on the twin-scroll turbos are divided into two parallel flow channels connecting with separate ducts in the exhaust manifold, allowing fine management of the exhaust gas coming in and pressure going out. Result is more torque and even better response times.

Drive goes to all four wheels via a new 'AMG Speedshift' nine-speed, dual-clutch auto (replacing the previous seven-speed auto transmission) with paddle shifters and a multiple downshift function which will go to the lowest ratio possible as you keep squeezing the shift paddle.

The 'AMG Performance 4Matic' all wheel drive system is front/rear biased 40/60 (50/50 in the previous model), although if you want to head off-highway the G 63 still features three 100 per cent diff locks and low-range off-road gear reduction.

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.

Claimed fuel economy for the combined (ADR 81/02 - urban, extra-urban) cycle is 13.1L/100km, with the 4.0-litre, twin-turbo V8 emitting 299g/km of CO2 in the process.

Despite the fact cylinder management tech means the engine will run on four cylinders under light load, and start-stop (with 'glide mode') is standard, we managed 16.7L/100km (measured at the bowser) over a mix of city, suburban and freeway running. To be expected for such a big bus, especially one that constantly tempts you into squeezing the throttle just to hear the exhaust bellow.

Minimum fuel requirement is 98 RON premium unleaded, and you'll need 100 litres of it to fill the tank.

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.

Let's cut to the chase. The G 63's pure grunt overpowers its challenging aero profile to thrust this boom box on wheels from 0-100km/h in a claimed 4.5 seconds. And believe it or not, despite its greater length and width, it has enough power to punch a 240km/h hole in the air (maximum velocity is limited to 220km/h if you choose not to opt for the 'AMG Driver's Package').

The new electronic architecture brings with it the latest version of Merc's 'Dynamic Select' system with five driving modes adjusting the engine, transmission, suspension, steering and assistance systems right up to maximum attack Sport+ mode.

All 850Nm of peak torque is available between 2500-3500rpm and pinning the throttle anywhere in that band feels like lining up a runway and preparing to rotate for take-off.

The two-stage exhaust flap arrangement allows you to turn the noise up from growl to roar even at modest around town speeds, and the nine-speed transmission is sharp and positive, with the multiple downshift function (in manual mode) hilariously good fun.

The racy AMG sports seats are as grippy as they are comfortable, and the fat 295/40 Goodyear Eagle F1 rubber, wrapped around the optional 22-inch forged alloys, does a good job of keeping all that mass and momentum in control as the high riding G 63 careens around corners.

And speaking of mass, the job of hauling it from warp speed to rest sits with big ventilated discs all around (cross-drilled 400mm front/370mm rear), clamped by monster six piston calipers at the front and single piston at the back. They're progressive and reassuringly powerful.

So, the performance is as dramatic as ever, but when I think of previous Merc-AMG G-Class offerings, two main shortcomings come to mind... steering and ride.

The steering was like a laggy mouse, with a few beats separating input at the wheel from response at the front treads. And the damping came up short, with a bouncy ride par for the course.

Still sitting on a ladder-type frame, the new G's suspension was developed by Mercedes-Benz and Mercedes-AMG. And finally, it has a decent double-wishbone independent front-end, with a rigid axle at the rear and coil springs all around. Plus, a strut tower brace, Merc-AMG calls it a 'suspension bridge', now connects the front strut towers, increasing torsional rigidity.

Ride comfort, especially in the most compliant 'Ride Control' suspension setting and riding on the big 22s, is massively better. It's no limo. You'll still feel jittering over higher frequency imperfections. But it's way, way ahead of the first-gen version.

The steering system changes from a recirculating ball to rack and pinion, and is now variable ratio with electro-mechanical rather than purely hydraulic assistance. And it's also much improved. We're not talking about a Lotus Elise-style connection with the road, but the steering is clearly more predictable and responsive.

One thing that hasn't changed is an ocean liner-worthy, 13.6m turning circle. You'll need to plan ahead for U-turns and reverse parks, but enough parking cameras (including surround view) to please Cecil B DeMille are on hand to help.

It's like a whole new world with a familiar cover wrapped around a markedly improved package. But (there must be a but) visibility is still compromised by thick window and door pillars, and despite the new dash layout ergonomic efficiency is patchy, with some switches and knobs located in relatively awkward positions.

As mentioned earlier the G 63 features three 100 per cent diff locks and low-range off-road gear reduction. But forget breakover angles and wading depths. This 4x4 seeing off-road action is as likely as an Abbott 2.0 prime ministership.

Suffice it to say, this car wears the 'Schöckl' badge at the base of its B-pillar. And in case you were wondering, Schöckl is a 1445m mountain in Graz, the Austrian city where the G-Class is built (and big Arnie Schwarzenegger was born!).

In the second-gen G-Class's development, prototypes covered roughly 2000km over a five kay trail including gradients of up to 60 per cent and lateral inclines up to 40 per cent. So, despite its irrelevance, the off-highway box is ticked.

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 (and by extension Mercedes-AMG) offers a three-year/unlimited km warranty with 24 hour 'Road Care' emergency roadside assistance provide for three years.

Servicing is recommended every 12 months/20,000km and a capped price servicing plan is available at Silver and Platinum levels for up to five years/100,000km.

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).