Audi S3 vs Mercedes-Benz SL63

What's the difference?

The updated Audi S3 Sportback is a fun-sized dynamo with impressive outputs and athletic road manners. It’s missing a few premium features, but its compact size paired with a gutsy engine makes it a compelling option for drivers who don’t want to compromise on performance (just space).

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.

The S3 Sportback may be a small car, but its S design features, like the stylised blackout grille, matrix LED headlights, and 19-inch alloys with red brake calipers, give it a distinctly athletic and fun-loving vibe. It’s compact, but definitely not diminutive and carries serious road presence. It’s hot hatch meets fun-size.

Inside, the S3 looks fabulous. Integrated ambient lighting, a sharp dashboard treatment and a driver-focused cockpit all lend it a premium feel.

The front seats look properly sporty with their integrated headrests, and the quilted Nappa leather upholstery feels great, especially with the eye-catching red contrast stitching.

As for technology, it’s as high-end as you’d expect with a 10.1-inch touchscreen multimedia display and 12.3-inch digital instrument cluster taking centre stage.

The only drawback? No sunroof. Combined with the black headliner and compact cabin, it can feel a little gloomy at times. Still, it’s a cabin you’ll enjoy spending time in.

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.

Like most hatches, the front row enjoys the most space. While it’s cosy, it never feels cramped. The seats are firm yet comfortable, thanks to their adjustability and expandable under-thigh supports. Access is fairly easy with wide door apertures, though the low seating position might earn a few grunts, especially from taller folks.

Storage up front is well sorted, with a glove box, a small centre console, a dedicated phone cradle and a couple of cup and bottle holders. It’s about what you'd expect for a car this size, but it's enough to keep things tidy.

There are plenty of charging options, with two USB-C ports in each row and a wireless charging pad up front.

The multimedia system is intuitive and easy to use. The touchscreen is responsive, and wireless Apple CarPlay connected without fuss and stayed connected all week. Wireless Android Auto is available, too.

Built-in sat nav is clear, and I love the way directions pull through to the digital instrument panel. The Sonos sound system? Pretty darn good. My son and I had more than one mini-concert on the school run.

As for the rear row, it definitely reminds you this is a small car. At 168cm, I found it on the cramped side of cosy and my husband just laughed when I asked him to try it! The wheel arch also cuts into the door aperture, making access a little awkward. Best to think of it as occasional adult seating. But given the size, that’s no surprise.

Amenities in the back are decent with a couple of map pockets, cup and bottle holders, as well as a fold-down armrest, those USB ports and rear temperature control (but curiously, no fan control). The seats are comfortable enough, but space is limited. Realistically, it’s best suited for two passengers, not three.

Boot space is quite practical. The wide opening and manageable load lip height make it easy to slide items in and out. It offers 325L of space, less than its key rivals, but expands to 1145L with the rear seats folded flat. The handy 40/20/40 split also adds versatility. Under the boot floor, you’ll find a tyre repair kit.

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.

Priced at $373,370, before on-road costs, the new SL63 4Matic+ will be battling top-shelf performance soft tops including (in ascending dollar order) BMW’s M850i xDrive Convertible ($307,100), the Porsche 911 Carrera GTS Cabriolet ($386,900) and even exotics like the Lamborghini Huracan RWD Evo Spyder ($422,606). 

Value for money is a relative concept in this part of the market, although equipment highlights include a head-up display (with augmented reality nav), 11-speaker, 650-watt Burmester surround sound audio, ambient lighting (choice of 64 colours), hectares of Nappa leather trim, dual-zone climate control, an 11.9-inch central multimedia screen (running Merc’s latest ‘MBUX’ software), 12.3-inch configurable digital instrument display and 21-inch forged alloy rims.

There’s also the ‘Digital Light System’ built around three high-power LEDs in each headlight, refracted and directed through 1.3 million ‘micro-mirrors’ to create a combined resolution of 2.6 million pixels.

The ‘Neck Scarf’ function is added to the top of the front seats to keep your neck and the back of your head warm as the temperature drops, the heated, ventilated and massaging front seats feature eight-way electric adjustment and three memories, there’s a heated steering wheel, Android Auto and Apple CarPlay connectivity, wireless device charging and more.

Worth noting the big 21-inch rims in a ‘10-twin-spoke’ design are standard issue with an alternate ‘multi-spoke’ pattern available as a no-cost option. 

But if all that’s not enough you can opt for ‘AMG Performance seats’ ($2490) which grip you even more securely but delete the massage function.

Or there’s the ‘AMG Night Package’ ($6990) which adds wheels in matt black (with “high-sheen finish rim flange”), darkened head- and tail-lights, an aero package, black badging, black radiator fins and interior trim elements in black chrome.

Then you can go the whole hog with the ‘AMG Carbon Fibre Package’ ($11,990) which brings the wheels in matt black, exterior carbon elements, carbon mirrors, carbon interior trim and a steering wheel in a combination carbon-fibre and Dinamica (synthetic microsuede).

The S3 Sportback wears the quattro badge proudly, meaning it’s all-wheel drive and it pairs a tweaked seven-speed automatic transmission with a 2.0-litre turbocharged, four-cylinder petrol engine.

This update brings a bump in performance over the previous model, including the addition of a rear torque splitter. Power is now up to a gutsy 245kW and 420Nm of torque, launching the S3 from 0 - 100km/h in just 4.7 seconds. That’s proper hot hatch territory.

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 S3 Sportback has an official combined fuel consumption figure of 7.9L/100km and a 55-litre fuel tank, giving it a theoretical driving range of up to 696km.

Its key rivals hover around similar numbers, so it's right on the mark for the segment. After a mix of long-distance drives and my usual urban errands, my real-world figure came in at 8.0L/100km - very close to the claim, which I’m pretty happy with.

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.

The S3 Sportback sounds as mean as it looks, and it delivers on that promise with effortless grunt. Acceleration is immediate, with plenty of power on tap when you need it. It’s just fun all around.

The lowered sports suspension and wide tyres do bring some extra noise into the cabin, even at lower speeds. You might find yourself repeating things to rear passengers now and then, but it never feels overwhelming.

Steering and suspension are on the firmer side, so yes, you’ll feel the bumps but the payoff is sharp, responsive handling. Quick lane changes and winding coastal roads are where this car shines.

Visibility is about what you’d expect from a low-slung hot hatch. The pillars don’t obstruct the view, but sitting beside a towering SUV at the lights can make you feel a bit... compact.

Cornering is a strong suit, thanks to the car’s wide stance and AWD system. It feels confidently planted in most conditions. That said, I noticed the occasional wobble through the rear frame on rough sections in heavy rain.

Its compact size makes parking a breeze, especially with the help of multiple sensors. The reversing camera is crisp, but at this price point, the lack of a 360-degree camera view feels like a missed opportunity.

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.  

No independent ANCAP safety assessment at this stage but the SL63 is fitted with the ‘Driving Assistance Package Plus’ which includes a heap of active (crash-avoidance) tech including AEB (with pedestrian detection), active cruise control, lane keeping assist, lane change assist, traffic sign assist, ‘Active Traffic-assist’ and ‘Active Steering Assist’. 

There’s also tyre pressure monitoring and the ‘Active Parking Assist with Parktronic’ self-parking system supported by a 360-degree camera view and multiple sensors. 

If a crash is unavoidable the airbag count runs to eight, including side bags for rear occupants. There are ISOFIX anchor points for child seats or baby capsules in the two rear and front passenger seat positions. And an active bonnet is designed to reduce injuries in the case of a pedestrian impact.

Audi backs the S3 Sportback with a five-year/unlimited kilometre warranty, which is on par with its European rivals. A five-year pre-paid servicing plan is available for $2890 which is cheaper than pay-as-you-go and reasonable for the class.

For those looking to go the extra mile, the 'Audi Advantage' package lets you extend the warranty and capped-price servicing by an additional two years, which represents solid value overall.

Servicing intervals are every 12 months or 15,000km, whichever comes first.

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.