Mercedes-Benz SL63 vs Porsche 718

What's the difference?

The new Mercedes-AMG SL63 4Matic+ is guaranteed to turn heads for decades to come. But there’s enormous design and engineering substance underpinning this car’s undoubted good looks. Stunning performance, superb dynamics and top-shelf safety make this a powerhouse GT to be reckoned with.

Note: CarsGuide attended this event as a guest of the manufacturer, with accommodation and meals provided.

If this is to be the end of the 718 as we know it, then it is an end to be remembered. Porsche has produced something special in the Spyder RS, a sports car that can compete with the 911 on any stretch of road - which is something so few cars can claim. The focus on performance has driven the entire concept of the car, but all the elements work in harmony, with form and function coming together.

Rather than a strict two-seater, this time around the SL adds the flexibility of ‘+2’ rear seating while the previous 'Vario’ folding hardtop has been binned, the new car returning to a traditional, electrically-folding and weight-saving (-21kg) soft top. 

Mercedes-Benz design chief Gorden Wagener started the new model’s development from a ‘clean sheet’ and Mercedes-AMG says “not a single component comes from the predecessor SL, or any other model such as the AMG GT Roadsters”. 

Always a subjective call, but I think this car’s proportions are just about perfect. The lengthy bonnet with its twin longitudinal ‘Power Domes’, raked windscreen and fat haunches create a wide stance and presence that’s almost impossible to ignore.

Aggression, as with the sinister headlights and 21-inch rims, is subtly combined with soft curves along the flanks and around the rear. Note the seamless door handles.

And it’s not all about aesthetics. Active aero has been integrated into the front apron and retractable rear spoiler. Plus the ‘Z-fold’ roof design does away with the need for a separate cover.

The interior is sub-zero cool with slick screens, an 11.9-inch display covering multimedia and a 12.3-inch unit for instrumentation ahead of the driver, being particular highlights.

Turbine-style air-vents at the leading edge of the split-level dash and alloy trim elements are a tip-of-the-hat to SLs past and the deft mix of large flat surfaces with complex curves oozes design confidence.

As the pinnacle of not only the current 718 range, but potentially the entire combustion engine era of the Boxster, Porsche has pulled out all the stops for the Spyder RS.

This includes major changes to the design, but none are purely for aesthetic reasons and instead are driven by the search for performance; and the fact they make the 718 look tougher, meaner and more purposeful than ever before is just a bonus.

It’s a comprehensive redesign that starts at the bumper with a new front lip spoiler to enhance downforce. Then there’s a pair of NACA ducts on the lightweight bonnet to improve brake cooling without compromising aerodynamic drag. The lightweight front fenders include wheel arch vents to stop any potential for front-end lift at high speeds.

And the fenders aren’t the only component that’s gone on a diet, there’s a lighter exhaust, lighter wheels, lighter bonnet, lighter roof, lighter door panels and even lighter carpets on the inside. All up, the Spyder RS tips the scales at 1400kg, which is 40kg lighter than a standard 718 Boxster.

If it’s still not light enough, you can opt for the optional 'Weissach Package' (which was fitted to our test car), which brings even lighter 20-inch forged magnesium wheels and carbon-fibre reinforced plastic for a range of parts including the front luggage compartment, rollover bars and ducktail spoiler on the Gurney flap – plus some cosmetic enhancements.

And we still haven’t even touched on the biggest design change yet - the rear half of the car. Starting with the roof, which Porsche actually calls a ‘sunshield’ and ‘weather guard’ because it’s a stripped down version of what the brand usually uses, to save weight and let the glorious engine noise into the cabin uninterrupted.

But it’s also necessary because the entire rear engine cover has been redesigned to accommodate the larger engine that Porsche has installed in the Spyder RS, a 4.0-litre six-cylinder instead of the usual turbocharged four-cylinder ‘boxer’ engines.

While the Spyder RS looks great with the roof/sunshield on or off, frankly the removal process is much too complicated and requires repeated viewings of a YouTube tutorial to still get it wrong.

While owners will (likely) eventually get the hang of it, it will always be a clunky and awkward process and that’s just the price of being so focused on performance, which you can accept or not.

Inside that ethos of performance over practicality continues, with sports seats, an Alcantara-wrapped steering wheel and even the previously mentioned lightweight carpet floor mats.

It’s a purposeful, rather than luxurious, cabin, but that perfectly suits the nature of the Spyder RS. Our test drive included several long stretches behind the wheel and at no stage did it feel uncomfortable or impractical, despite its stripped-down design.

In the context of a high-performance GT, practicality is pretty impressive.

At just over 4.7m long the SL is a sizeable machine and much of its lengthy (2700mm) wheelbase is devoted to making the driver and front passenger comfortable.

There’s plenty of space for that pairing and just enough storage to cope with the ‘things’ they’ll typically bring with them.

Door pockets offer enough room for a few odds and ends, although you’ll struggle with even a medium-size bottle unless you’re willing to lay it down horizontally along the top of the aperture.

A handy lidded bin between the front seats doubles as a centre armrest, there are two cupholders under a sliding lid in the centre console and the glove box is a decent size. 

Power and connectivity options run to four USB-C ports, a 12-volt socket and the wireless device charging pad.

Then there are the rear ‘+2’ seats, and Mercedes makes no bones about the fact they’re intended for occasional use only, even suggesting a 1.5m occupant height limit.

And there’s no doubt they offer a handy emergency seat or a fun kids’ zone. Just ask a Porsche 911 Carrera owner how much this kind of seating arrangement increases a sports car’s flexibility.

At 183cm I gave the back seat a crack, which meant sliding the front (passenger) seat way forward with the backrest close to upright. But I squeezed in, and there was just enough legroom for a person in front at the same time. 

With the roof in place there’s the added pleasure of cranking your head over to around 45 degrees. But it’s do-able! 

No storage, adjustable ventilation, or power back there. But that’s fair enough, especially given there are USBs available in the front centre storage box.

Boot volume is 240 litres with the roof up and 213 litres with it folded, which is enough for some light luggage, and not too shabby when you think a Toyota Corolla hatch offers up just 217 litres (with all seats up).

There’s a 12V socket in there, but don’t bother looking for a spare, in the event of a flat your only option is a repair/inflator kit.

One area where the 718 range is starting to show its age quite dramatically is the in-car technology. While Porsche’s native system is relatively user-friendly, the lack of wireless Apple CarPlay or Android Auto in any capacity is deeply out-dated; and was frustrating for this Android using reviewer.

Given the age of the current 718 platform, and the impending arrival of the new model, it’s understandable that the multimedia system didn’t get an overhaul, but for a $350K car it does feel a bit behind the times.

In practical terms the Spyder RS is a bit of a struggle if you plan to go away with it. We managed to get a small suitcase and backpack in the under bonnet storage, but that was at capacity. While the addition of the larger engine removes any meaningful rear storage space.

The bad news is, the Spyder RS costs just over $200,000 more than the entry-level 718 Boxster, which is not a small sum of money. The good news is, for that $200K, Porsche has overhauled the 718 from nose-to-tail and enhanced it in nearly every aspect.

There’s a raft of mechanical changes that we’ll get to later on, to help justify the $334,200, plus on-road costs, asking price, but from a specification perspective there are some notable inclusions. 

For starters it comes with the 'Porsche Communication Management' (PCM) multimedia system, which includes in-built navigation and Bluetooth connectivity, as well as a 110-watt sound system.

But Australian delivered cars get an even higher level of standard equipment than other countries, with LED headlights including 'Porsche Dynamic Light System' (PDLS), cruise control, digital radio, rear 'ParkAssist' with reversing camera, 'Light Design Package', tyre fit set and windscreen with grey top tint, plus a no-cost optional Bose Surround Sound System all included.

It may be $200K more than 718 but compared to a 911, it actually makes a pretty compelling value argument. A 911 Cabriolet Carrera S starts at $342,700 (plus on-road costs), making that Spyder RS $8500 cheaper and a genuine alternative to its ‘big brother’.

Then, when you compare it against similar mid-engine European sports cars, such as the Maserati MC20 (from $510,000) or McLaren Artura (from $477,310) the Porsche looks like a bargain; relatively speaking, of course.

This new ‘4Matic’ all-wheel-drive SL63 features AMG’s (M177) 4.0-litre twin-turbo V8, superseding the previous rear-wheel-drive SL’s similarly configured 5.5-litre unit.

Hand built by one AMG technician from start to finish, it produces 430kW (around 580hp) from 5500-6500rpm and 800Nm across a broad plateau from 2500-5000rpm.

It’s something of a mechanical masterpiece, and the previous seven-speed auto transmission, driving the rear wheels only, has been replaced by a nine-speed dual-clutch auto (with wet multi-disc start-off clutch) sending drive to all four wheels via Merc’s ‘4Matic’ AWD system.

The key stat for the engine is the cylinder count. Gone are the four cylinders and instead it’s a return to Porsche’s iconic flat-six.

Specifically, the same 4.0-litre six that Porsche uses in its 911 GT3, which is a lot of engine to squeeze into the middle of this lightened sports convertible.

In order to keep the 718 in its place (beneath the 911), Porsche has slightly detuned the engine, so it makes 368kW/450Nm (compared to 375kW/460Nm in the 911 GT3), but the German brand has never worried about a kilowatt contest and instead prefers to focus on driveability and the other elements that make a drive great.

To that end the combination of air-intakes next to the headrests and the lightweight stainless steel exhaust (which gets titanium tips on the Weissach Package) helps the Spyder RS sound like a Carrera Cup racing car when you really wind it up to its 9000rpm redline.

Not that the performance isn’t spectacular, though, with Porsche claiming it takes the Spyder RS just 3.4 seconds to run 0-100km/h, only 10.9 seconds to get from 0-200km/h and will hit a top speed of 308km/h.

The engine is paired to a seven-speed dual-clutch auto transmission (or PDK in Porsche-speak) that the company claims has “short-ratios”, but with peak power not hitting until 8400rpm and peak torque from 6750rpm, you don’t have to rush the ratio changes.

Mercedes-AMG’s official fuel economy number for the SL63 on the combined (WLTP) cycle is 13.9L/100km, the 4.0-litre twin-turbo V8 emitting 319g/km of CO2 in the process.

On the roughly 300km launch program we covered urban, B-road and some freeway running, returning an (indicated) average of 17.5L/100km. And that reflects some enthusiastic driving along the way.

The fuel tank requires 70 litres of 98 RON premium unleaded to fill it which translates to a theoretical range of around 500km, dropping to 400km using our real-world number.

Porsche says the 4.0-litre engine in the Spyder RS uses 13.0L/100km, which is a big number for what is a relatively small car. But that engine is highly-tuned and built for performance not efficiency, so it’s something owners will need to accept.

Our test drive included some long highway stretches, as well as some spirited driving and urban commuting, so a good mix across all conditions, and we saw consistent returns around the 15-16L/100km range.

It has a 64-litre tank, which means a theoretical driving range of around 490km, assuming you can hit the official claim.

I recall driving the AMG SL65 around the backroads of Tassie a few years ago and that twin-turbo V12 monster famously packed 1000Nm of torque, while this car ‘only’ has 800.

But there comes a point where enough is enough… and this is enough!

With maximum torque available from 2500-5000rpm and peak power (430kW) on call from 5500-6500rpm there’s always stupendous acceleration available with a squeeze of your right foot.

Claimed 0-100km/h time is supercar fast at 3.6 seconds, while top speed is a toupe-troubling 315 km/h. And that’s electronically limited!

A typically ferocious engine noise and howling exhaust note accompany rapid progress and shifts from the nine-speed dual-clutch transmission are quick and positive, not to mention especially enjoyable using the steering wheel-mounted paddles.

There are six ‘AMG Dynamic Select’ drive programs from Comfort through to Race, the latter including a Drift Mode, which we didn’t experiment with. Nor did we dip into the ‘AMG Track Pace’ system for circuit-focused mapping and timing

However, far from drifting, the grippy Michelin Pilot Sport 4S rubber (275/35 fr - 305/30 rr) plants the car securely with the all-wheel-drive system and electronic locking rear diff playing their part.

I found the perfect set-up was in the ‘Individual’ mode with the engine, transmission and steering in racier settings and the suspension in ‘Comfort’. The adaptive damping in this configuration mixes smooth ride compliance with sharp dynamic response.

The car’s aluminium space frame chassis is part of a body structure mixing aluminium, magnesium, fibre composites and various strength steels.

Torsional rigidity is claimed to have been improved by 18 per cent and despite the lack of a roof the SL feels tight and solid.

Suspension is by alloy double wishbones front and rear with adaptive damping and active hydraulic anti-roll stabilisation standard (so, no physical anti-roll bars).

At the same time the 4Matic AWD system is able to vary torque distribution up to 100 per cent to the front or rear axle depending on where drive can be put to best use.

The speed sensitive, variable ratio, electronically controlled steering is accurate and turns in beautifully with good road feel. No doubt assisted by electric rear steering able to adjust the angle of the rear tyres by up to 2.5 degrees.

All this adds up to a hugely impressive package that, despite its 1970kg kerb weight, feels agile, athletic and able to attack corners like an overgrown hot hatch, putting its power down with unwavering authority.   

While indecently fast the SL63 can also stop rapidly with the AMG high-performance braking system standard. 

Huge composite ventilated and cross-drilled discs (390mm fr - 360mm rr) are clamped by six-piston fixed alloy calipers at the front and single-piston units at the rear. They wash off speed calmly and consistently with perfect pedal feel.

Even at highway speeds, particularly with the windows up, normal conversation is easy with the roof down. But if you need to raise (or lower) it, the operation takes 15 seconds and is possible up to 60km/h. 

Under the heading of miscellaneous observations, the turning circle is a not insubstantial 12.8m, so beware in the car park.

A front axle lift function is a welcome standard feature, raising the car’s nose 30mm with the press of a button. And lift locations are stored in GPS data, so the car will subsequently remember to lift itself at the same place, even if you don’t! 

Heating and cooling for the front seats combined with the heated steering wheel and Air Scarf neck warming makes winter top-down driving a pleasure.

The digital instrument display is not only crystal clear, it can be changed through multiple configurations, including a tunnel-like graphic for engine revs as well as specific readouts for speed, g-force, the lot.

At the same time, the central media screen’s angle can be adjusted to better cope with reflections and the windscreen wiper system Merc calls ‘Magic Vision Control’ channels fluid along the wiper arms onto the rubbers, which isn’t new, but works spectacularly well here.  

I’m only giving it a nine out of 10 because perfection is hard for any car to achieve, but the 718 Spyder RS goes as close as any car I’ve driven. This is a masterpiece of modern sports car design, pushing the 718 closer to the 911 than ever before, which is something Porsche has clearly tried to avoid so as to not tarnish the image of its flagship.

But with the 911’s 4.0-litre flat-six in the middle of the 718, plus its more compact dimensions, the lightweight nature of the Spyder RS and the raft of chassis and handling enhancements, this really does leave you questioning ‘do I really need a 911?’

The steering is fantastically direct, the chassis responds to every input with precision and feedback and the braking is strong and consistent. Which helps because that engine is so good it launches you with ferocity and a glorious noise (as good as anything on the market today) whenever you squeeze down on the accelerator.

The highest praise I can give the Spyder RS is not that it was a dream to drive on winding, challenging roads, but that it was just as enjoyable on a trip to the shops or cruising down the freeway. Any drive in this car is a genuine pleasure.

This is another area where the 718 is showing its vintage, with very little in the way of active safety features. There’s the required stability control, as well as airbags for driver and passenger, plus the previously mentioned reversing camera. But that’s it, there’s no autonomous emergency braking, no lane-keeping assist or even adaptive cruise control.

While that may sound shocking to some, there’s never a moment where you feel unsafe in the 718. It feels incredibly stable and responsive on the road, as the onus falls back upon the driver to pay attention and make smart choices.

There’s no ANCAP rating for the 718, or any Porsche, so it is a question of putting your faith into Porsche’s in-house safety measures.

The SL63 4Matic+ will be covered by Mercedes-AMG’s five-year/unlimited km warranty, with roadside and accident assistance included for the duration, both of which are expected in this category. 

Maintenance intervals are 12 months/20,000km, and a fixed-price service plan lists an average of $1583 for each of the first three visits to the workshop. Not exactly small change, but not unheard of in this part of the market.

It’s difficult to give the Spyder RS a clear score here because Porsche is cagey on the details. The public dealer websites indicate annual oil maintenance is required, with additional servicing every two years or 15,000km. 

How much that will cost is unclear, as despite the rest of the 718 range having publicly available prices, there were no such details for the Spyder RS (or even its Cayman sibling, the GT4 RS).

For reference, the 'standard' 718 requires oil maintenance ($895) for the first annual service and an inspection ($1500) the year after. Those costs continue to alternate annually out to eight years/120,000km.