If you’re expecting a cosseting cruiser from the Mercedes-AMG SL, think again. The clue is in the name, with all versions of the SL being developed by in-house performance arm AMG this time around. That means a leaner SL, one that’s trying to be a sports car, that should be more than happy hammering over challenging B roads whilst serving up a few thrills.

Despite this, the latest SL is in some respects more practical than before, with a couple of occasional rear seats crammed in. The downside is a serious reduction in boot space, although we suspect many will use the back seats as an additional luggage store, a trick known to Porsche 911 Cabriolet drivers the world over.

Ah yes, the 911. Although the SL is significantly heavier, it’s much closer in spirit to Porsche’s most famous export than its predecessor. Other rivals include the Bentley Continental GT Convertible, BMW 8 Series Convertible and the Aston Martin DB12 Volante.

Like the Bentley, the SL is available with an obscenely powerful plug-in hybrid system with a turbo V8 at its heart. We’ve tried this and all the other engine options to give you our definitive verdict. If you’d like to know how we draw our conclusions, check out our how we test cars page.

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What’s it like inside?

The flashy cockpit is rammed full of smartphone style tech, but unless you have a knack for touching, swiping and zooming through life, the MBUX infotainment software takes a while to reveal its full potential. You really do control almost everything through the screen including the roof and climate controls. The latter are permanently displayed at the bottom of the screen making them only slightly annoying, but the roof is harder to find and operate. Not good considering you can raise or lower at up to 37mph.

The touchscreen’s graphics are certainly sharp, hardware responsive and menus not too hard to fathom, but we’d kill for a few more physical buttons. The screen can be tilted more or less upright to account for the sun’s glare with the roof down, but this feels like a sticking plaster to fix the inherent problem of such a large, angled touchscreen without any sort of cowl.

If you don’t like prodding the screen, the SL comes with Mercedes’ impressive voice control system that’s surprisingly accurate. It’s preferable to using the touch-sensitive steering wheel which proves fiddly and too easy to activate when you’re twirling the wheel. With so many buttons crammed onto the four-spokes, there’s no telling what you’ll turn on or off, either.

Quality is for the most part good, with plenty of leather, contrast stitching and, on our test car, carbonfibre trim. Look closer and you’ll find a few disappointing materials that mean the BMW 8 Series Convertible, let alone the Bentley Continental GT feel plusher inside. The cabin is available with supportive massage seats, heated door panels and armrests, standard neck warmers and some very colourful ambient lighting.

As for space, those up front will have no reason to grumble even with the roof up. The rear seats are definitely best left to children, with even our shortest 5′ 3″ road test elf feeling hemmed in. Even so, you might struggle to fit a bulky Isofix seat back there, certainly with tall occupants up front.

Indeed, a tall driver pushing their seat back soon eliminates rear legroom entirely. The 213-litre boot expands to 240 litres when the roof is up, which is enough to carry a couple of squishy bags, but is well below most rivals.

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What’s it like to drive?

There are four engines available – an entry-level four-cylinder, a V8 with two power outputs, and a V8-based plug-in hybrid. If you’re worried about the reduced cylinder count of the SL 43 hurting power, don’t be. This is the same 2.0-litre turbo lump found in the AMG A 45 and here makes 421hp, enough for a 4.9 second 0-62mph time. You need to work the engine hard for that performance.

The SL 55 and SL 63 both get a 4.0-litre twin-turbo developing 476hp and 585hp respectively. Even the 55 has plenty of punch – enough to allow it to complete the 0-62mph sprint in 3.9 seconds, just 0.3 seconds behind the 63. The 63 does feel appreciably faster, if not as bonkers as the 63 S E Performance.

This pairs a 612hp version of that V8 with a 204hp electric motor. There’s no fudging of numbers, with maximum poke the full 816hp giving 0-62mph in a jaw-dropping 2.9-seconds. It keeps pulling well beyond that, with a stretch of clear Autobahn allowing 170mph to be reached quickly and with unwavering stability. Expect a real world electric-only range of a mere six miles and no attractively low BIK payment, either.

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The S E Performance weighs 300kg more than the already two tonne plus V8 models, and you’re aware of the bulk under heavy braking and quick direction changes despite loads of clever chassis tech. The rear-wheel steer, an electronic rear limited-slip diff and roll-limiting suspension do make for some exceptionally high limits, even if the regular 63 that shares the tech is happier on a twisty road.

There are a number of drive, transmission and suspension modes to choose from in all models. If you want the most exciting time, Race mode gives you the fastest shift speed, the quickest steering response front and rear, the most controlled damper setting and the most responsive throttle action.

When testing on a challenging route, the transmission can be a little off-the-pace – third gear covers most twisting roads, but sometimes when second is needed, the short gearing can leave it revving a little too hard. Although there are nine ratios to choose from, the first three feel too low to feel any benefit aside from super-quick launches. Thankfully a manual override is easily activated.

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The SL43 is usefully lighter than the V8 cars on account of its smaller engine and rear rather than four-wheel drive, but doesn’t sound anywhere near as good . It is after all, the sound of a hot hatch. It feels the most natural to drive of the bunch with a suppler edge and easier to find limits, making it arguably more fun more of the time on the road.

The Active Ride Control suspension – standard on 63 and 63 S E Performance with steel springs, adaptive dampers and hydraulically adjustable anti-roll bars – is definitely set to the firmer side of comfortable, even in its squishiest mode. You’ll feel ridges and potholes, but the suspension works well to take away the initial shock, so long journeys shouldn’t be too taxing on your back. Plentiful tyre roar does mean your ears take a bit of a battering, but it’s no worse than a 911.

You’ll want to quickly disable the overly-keen lane-departure system, something that is best done when stationary as it’s a few screen prods away. With it off, you’ll find the steering is precise with a suitably beefy weighting, although a 911’s wheel communicates better with the driver.

The rear steering that comes with the 55 and 63s helps boost agility at low speeds and stability at high speeds, but neither this nor the active anti-roll bars can fully hide the width and heft of the car. A non-hybrid 63 is certainly keener than its predecessor and has far greater traction thanks to the all-wheel drive, but a 911 remains the more entertaining drive.

Apart from the road noise, suspension thump is the only persistent acoustic intrusion. The soft-top is quiet when closed, doing an impressive impression of a solid roof.

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What models and trims are available?

Along with the four current engine choices, there are five trim levels to pick from. Entry level Premium and second-rung Touring models are only available with the four-cylinder 43, while Ultimate is 63 only. Touring Plus is 43 or 55 V8 while Premium Plus is available as a 43, 55 and 63.

Essentially, Premium and Ultimate are the sporty looking ones with black exterior detailing, wheels and interior. Touring models get chrome on the outside with silver wheels and beige leather with aluminium trim inside. All models get heated electric memory front seats, heater vents in the headrest or Airscarf in Mercedes terms, keyless entry and start, all-round parking sensors and cameras, a Burmester stereo and Nappa leather seats.

We’d be tempted to go for a Plus trim to gain a heated steering wheel, massage front seats, a head-up display and some very handsome 21-inch wheels. V8 55 and 63 models also gain upgraded headlights, rear-wheel steering, carbon fibre interior trim and cooled front seats. Ultimate models gain forged wheels, ceramic brakes and an AMG aerodynamics package.

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