Glendal's Favorite Reviews: Porsche 911 Cabriolet vs Mercedes-AMG GT Roadster

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2019-08-20 16:15

The brand new Porsche 911 Cabriolet takes on the updated Mercedes-AMG GT Roadster

Porsche 911 Cabriolet vs Mercedes-AMG GT Roadster - header

With summer in full swing, there’s a number of new high-profile convertibles hitting the market, starting with the Porsche 911 Cabriolet. This drop-top follows in the wheeltracks of the Coupé, with the famous sports car now in its eighth generation.

There’s also much more tech underpinning the 911’s new platform, while Porsche has worked hard to reduce the impact of removing the 911’s roof and make this a car that’s befitting of that badge when it comes to the driving experience.

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After more than 50 years of evolution, the 911 in all its forms has staved off the challenge of its rivals. But with this 992 Cabriolet they’re still coming thick and fast, the latest in the form of the updated-for-2019 Mercedes-AMG GT Roadster. The recipe here is traditional AMG, with a V8 engine up front powering the rear wheels for what, we hope, is a beautifully balanced drive.

Both cars have electrically folding fabric roofs, a top speed of 188mph and a price tag comfortably exceeding £100,000. Yet they approach the brief for an exclusive cabrio in decidedly different ways, so let’s find out which is best.

At this level of the market, with cars costing this much, buyers will forgive few faults, so it’ll be an incredibly tough test.

Porsche 911 Cabriolet

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Model:	Porsche 911 Carrera 4S Cabriolet
Price:	£109,398
Engine:	3.0-litre flat-six twin-turbo, 444bhp
0-60mph:	3.3 seconds
Test economy:	22.1mpg/4.9mpl
CO2:	207g/km
Annual road tax:	£465

We’re testing the new Carrera 4S version of the 911 Cabriolet here. So while it’s four-wheel drive when compared with the rear-driven AMG, it brings their respective prices closer for parity, at £109,398. It’s a chunky price tag, but is it worth it?

Design & engineering

Like the 911 Coupé, this 992-generation Cabriolet is based on a new platform that includes more aluminium than ever before to help keep kerbweight down. This stands at 1,635kg for this Carrera 4S, which is unsurprising given the 911’s increase in size over its predecessor.

The Cabriolet is currently offered in Carrera, Carrera S and Carrera 4S guises, all with Porsche’s eight-speed PDK, dual-clutch automatic gearbox – a manual box is promised at a later date.

All models get a 3.0-litre twin-turbo flat-six that’s an evolution of the engine seen in the 991.2 model. New turbos (now specific to each cylinder bank) and updated cooling and injection systems in the latest unit have helped liberate more power and torque, so there’s 444bhp and 530Nm on offer in the 4S.

The transmission is also new, with eight ratios and space inside the gearbox for an electric motor, so hybrid variants of the 911 are in the product plan.

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The 911 has a wider track front and rear, which has created a little more space inside, while Porsche’s approach to the interior has changed tack with the 992. There’s a lot more tech, and the infotainment screen and major controls are arranged horizontally in two layers, rather than the central stack of its predecessor. It works well; the ergonomics are good and the driving position superb – the AMG GT is more compromised.

Removing the roof has obviously required some chassis strengthening to retain as much structural rigidity as possible, and while the Cabriolet is 70kg heavier than the coupé, it also adds to the experience.

You can drop the roof electrically in 12 seconds at up to 30mph, while the canvas features extra insulation to improve refinement. That’s an element that’s been improved for this new car, while there’s also more standard kit – and so there should be at this price.

Sat-nav, Apple CarPlay, LED lights, heated seats, adaptive suspension, parking sensors, a reversing camera, AEB, climate and cruise control are all standard.

Driving

A huge part of any cabriolet’s appeal centres on the roof-down driving experience, and the 911 is about as complete as they come.

Convertibles are partly about basking in the exhaust note, and while the AMG offers a superbly characterful V8 bellow, the 911’s soundtrack isn’t quite as rich, even with the £1,844 sports exhaust fitted. The bassy bark is overlaid with turbo noise – it’s the way 911 development has gone, but it does mean there’s plenty of performance.

Despite a 32bhp power deficit and 100Nm less torque than the AMG, the 911’s excellent launch control and four-wheel-drive traction meant it romped from 0-60mph in 3.3 seconds.

With an extra ratio in its gearbox, the 911’s in-gear times are slightly skewed against the Mercedes’, but the Porsche feels equally potent. The gearbox is great, with sharp changes and no perceptible interruption to drive. Downshifts are beautifully smoothed out with an automated blip. There’s a little more lag than the Mercedes, but the engine is torquey and linear.

Where the 911 really shines compared with the AMG is in the way it rides and handles. It’s firmer, but much more comfortable, while the inevitable body shake you get from a convertible is well contained.

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Even in the firmer of the two suspension modes the damping feels slicker, finessing bumps that the AMG thunders over. It’s impressively composed and generates more grip than the Mercedes. You also know more about the grip level and have a better connection with the car thanks to the steering – the weighting in particular is much more natural.

Practicality

Convertibles like these generally see practicality as a secondary concern, with usability centring more on features like the 911’s wind deflector. It’s electric and does a good job of reducing turbulence when the roof is down.

Of course, with two small back seats for kids or extra luggage, the 911 has a little more practicality than the Mercedes, even if the 132-litre boot in the nose is less than the GT’s claimed 350-litre maximum.

Ownership

Porsche didn’t rank in our Driver Power owner satisfaction survey this year. However, given that much of the 911’s tech is shared with other models – its infotainment is similar to the Cayenne and Panamera’s, for example – and the 3.0-litre engine proved to be reliable in the previous-generation 911, then this 992 should be no different.

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There’s more safety tech on offer than ever as well. Autonomous braking is fitted, there are six airbags plus pop-up roll bars that deploy from behind the rear seats if the electronics sense that the car is going to flip over, as with the GT. Lane-keep and blind-spot assist are optional, at £749 and £581 respectively.

Running costs

Fuel economy won’t be much of a concern for buyers looking at a £100,000-plus convertible sports car. But cruising range might, and both cars here are similarly matched. The 911 returned 22.1mpg, and with a 67-litre tank will manage a max 326 miles on a run.

The AMG GT did slightly less well, at 20.9mpg, but will cover around 345 miles thanks to its larger fuel tank. Petrol costs based on these numbers stand at £3,253 and £3,440 for 12,000 miles of use.

Testers’ notes: “How can you tell the difference between the rear-wheel-drive Carrera S and the all-wheel-drive Carrera 4S in our pictures? Simple, the latter has silver air vent slats on the engine cover.”

Mercedes-AMG GT Roadster

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Model:	Mercedes-AMG GT Roadster
Price:	£115,875
Engine:	4.0-litre V8 twin-turbo, 469bhp
0-60mph:	4.1 seconds
Test economy:	20.9mpg/4.6mpl
CO2:	261g/km
Annual road tax:	£465

A facelift for the Mercedes-AMG GT Roadster has kept it fighting fit against newer rivals like the 911 Cabriolet, with some significant updates to improve its appeal. At £115,875 it’s dearer than even the 911 Carrera 4 S Cabriolet, but price isn’t as much of an issue as ability at this level.