Mercedes-Benz Gls450 vs Porsche Cayenne

What's the difference?

The GLS450d impresses as an entry-level grade, as it’s a more family-friendly allrounder than the specialised AMG and Maybach variants. Its combination of a torque-rich diesel 48V hybrid drivetrain, air-cushioned suspension and plush interior are as well suited to luxury urban travel as they are to grand touring, where its heavy towing and generous load-carrying capabilities can shine. Whether it’s worth around $200K drive-away, only those who shop at the top end of town can decide.

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.

This is an imposing vehicle in extravagant S-Class tradition, riding on an expansive 3135mm wheelbase and stretching more than 5.2 metres (5215mm) long and more than 2.0 metres (2030mm) wide with a turning circle that's nudging 13 metres.

However, it’s just under 1.8 metres (1798mm) tall, so there’s no clearance issues when accessing multi-storey carparks. And with its side-steps (or ‘running boards’ in nostalgic Benz speak) most adults can step rather than climb aboard, although passengers of shorter stature during our test noted that assist handles on the A and B pillars would be handy.

Central to its sophisticated chassis design is adaptive air suspension, which uses a pneumatic or ‘airbag’ form of springing with adaptive damping to continuously optimise ride comfort and handling response according to road conditions and driving dynamics (see Driving).

The GLS’s styling is clean and uncluttered with tasteful restraint evident in its chrome and satin-chrome highlights, yet it projects a majestic quality with its prominent four-louvre grille and elegantly spoked alloy wheels.

The spacious and sumptuous seven-seat interior is visually pleasing and practical, with a subtle blend of surface treatments, contrasting tones, lots of soft-touch surfaces and exposed stitching. This is combined (thankfully) with physical dials, switches and ‘piano key’ buttons to control numerous interior functions, in preference to distracting touchscreen prompts.

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.

Although it has a hefty 2655kg kerb weight, our test vehicle’s 3420kg GVM rating provides a useful 765kg of load capacity, which should comfortably absorb the combined weight of up to seven occupants and light luggage. Or with the third row of seating folded, five occupants and heavier luggage.

It’s also rated to tow up to 3500kg of braked trailer and with its sizeable 6920kg GCM (or how much weight it can legally carry and tow at the same time) it can carry its maximum load while towing its maximum trailer weight.

So, that’s commendable practicality, given it would be well suited to owners that need to tow large caravans, boat trailers, horse floats etc in style without having to compromise much (if at all) on either passenger numbers or luggage capacity.

Driver and front passenger space and comfort is exceptional, as you’d expect. Storage includes a large glovebox plus a bottle holder and bin in each door. The front of the centre console has two USB-C ports, wireless phone charging and heated cupholders, while the rear of the console has a large storage box with a third USB-C port and padded lid that doubles as a comfy elbow rest.

Even tall passengers in the second row of seating enjoy spacious comfort, given I’m 186cm and with the driver’s seat set in my position I have ample knee clearance, foot room and head space.

However, the central passenger must contend with a transmission tunnel in the floor and shoulder room would be squeezy for three large adults, which is okay for short trips but a maximum of two would be ideal for longer journeys.

The rear of the centre console also treats second-row passengers to a pair of USB-C ports, adjustable air-vents and a control panel that allows independent climate adjustment.

There’s also a large bin/bottle holder in each door plus storage nets on each front seat backrest. The centre seat backrest folds flat to allow long items (skis etc) to slot between the outer backrests. And it also serves as a fold-down armrest, containing two cupholders and a lidded slimline compartment that’s ideal for hidden phone storage.

The third row is uncommonly spacious, even for tall people, with padded armrests on each side containing cup holders and twin USB-C ports.

The carpeted rear luggage area has four load-anchorage points, a first aid kit and 12v socket. With the third-row seats upright it offers 355 litres of load volume, which increases to 1350 litres with the third row folded and 2400 litres (or 2.4 cubic metres) with both the second and third rows folded.

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 GLS450d comes standard with a 3.0-litre turbocharged inline six-cylinder diesel producing 270kW of power at 4000rpm and 750Nm of torque between 1350-2800rpm.

This is paired with a 48V mild-hybrid system comprising a 48-volt battery (charged by regenerative braking) and an integrated starter-generator which provides both seamless engine stop-start and up to 15kW/200Nm of extra power and torque during acceleration.

A nine-speed torque converter automatic provides the choice of manual shifting using the steering wheel-mounted paddles, along with several selectable drive modes.

The active all-wheel-drive system continuously adjusts the engine’s torque delivery between front and rear axles (and individual wheels as needed) to maintain optimum traction and handling.

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-Benz claims official combined consumption of 7.8L/100km and the dash display was showing 9.0 when we stopped to refuel at the completion of our 368km test, which included the usual mix of suburban, city and highway driving with up to five passengers at times and light luggage.

Our own figure, calculated from fuel bowser and tripmeter readings, was close at 9.5 which is outstanding sub-10L/100km economy for such a substantial vehicle in mostly metropolitan use. Therefore, based on our own consumption figure, you could expect a real-world driving range of around 950km from its 90-litre diesel 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.

It’s an enjoyable vehicle to drive, with multiple power adjustments for the seat and steering wheel combined with a large left footrest which provide supreme driver comfort and support.

The powerful and responsive turbocharged six-cylinder diesel and nine-speed auto are well suited to this application. The engine’s ample torque provides spirited acceleration from standing starts, taking only six seconds to reach triple-digit speeds.

This drivetrain would be well suited to heavy towing duties, given the 48V mild-hybrid system can contribute an extra 200Nm (in addition to the engine’s 750Nm), which raises the total theoretical torque output to almost 1000Nm.

The active air suspension provides a wonderfully cushioned ride that floats over bumpy roads, while maintaining excellent handling response and surprising agility. These commendable chassis dynamics, combined with the powerful and responsive drivetrain, makes the vehicle feel smaller and lighter than its dimensions and kerb weight would suggest.

Overall, it’s difficult to fault from a driver’s perspective, with the only exception being the voice activation function. This is often triggered by words or phrases other than ‘Hey Mercedes’ resulting in regular interruption of conversations. This needs some fine tuning.

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.

The GLS comes with a five-years/unlimited km warranty (better than BMW and Lexus) and five years of roadside assistance. Scheduled servicing is every 12 months/25,000km whichever occurs first.

Mercedes-Benz offers capped-price pre-paid servicing packages with three, four or five-year terms. For example, the total upfront cost of the minimum three-year term is $4090, or an average of $1363 per service.

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).