Audi RS5 vs Mercedes-Benz SL-Class

What's the difference?

Good looking, good to drive, and good to simply sit in, the Audi RS5 range ticks plenty of premium boxes. Whether you can live with the practicality pitfalls of the Coupe is up to you, but if you can't, might I suggest taking a wander over to our RS4 Avant review?

The SL's overall score is somewhat skewed by everyday concerns, and rules are rules - an average punter will find the price of this car somewhat confusing and the devil-may-care attitude to fuel consumption bewildering.

If neither of these things are a problem, then the SL63 makes plenty of - well, not sense, because it's not a particularly clever or considered car - but it fills a niche that not so long ago we all thought would go the way of the dodo.

The fact it sells so few examples is betrayed by some of the cabin amenities and the fact that Mercedes hasn't put much effort into reducing the car's weight to improve its consumption or sharpen up the handling.

The fact it still exists at all is pretty damn cool, though, and for certain people an SL63 purchase is the culmination of a lot of hard work.

If it is your dream car, the SL63 won't disappoint. Everyone who rode with me said it was mightily impressive, but you've got to really want it. When you're not far off buying a Ferrari California T or Aston Martin V12 Vantage S for the money, you'll need a real yearning for the three-pointed star to go this way. And if you do, good luck to you - you've probably worked quite hard to get here.

I defy anyone to describe the RS5, and especially the Coupe, as anything but stunning. Seriously, the near perfect proportions and swept-back styling make it look fast even when it's parked. 

Up front, there's a new-look black-mesh grille that's been given a 3D effect, like it juts out over the road in front it, while the thing headlights have been carved back into the body work like they're been windswept under hard acceleration.

The 20-inch darkened alloys fill the arches, too, with a sharp body crease that runs from the front headlight all the way back to the bulging shoulder lines above the rear tyres accentuating the curves.

Inside, the RS5 is a sea of black Nappa leather and sporty touches, and we particularly like the chunky, flat-bottomed steering wheel, which both looks - and feels - great.

The SL has always been completely unapologetic about its size and seems to be designed to accentuate rather than hide its length and width. The long bonnet screams power and prestige, and get out of my way, and is reminiscent of the little-loved McLaren SLR project of some years ago.

The size of the Mercedes logo on the huge front grille leaves you in little doubt about the brand of car that’s about to pass you at speed and some might say (okay, I would) that its large surface area is a little vulgar.

Like the SLR, the design doesn't seem to have a particularly cohesive strategy, with a number of Mercedes elements from around the traps that climb over each other. Roof up it looks awkward because of the gigantic posterior while with the roof down it looks overly long and, again, tail-heavy.

Folding hardtops are notoriously cumbersome and need a lot of room to hide them, but the silent operation is something to behold.

Elements that are worth deleting if possible are the dodgy 'Biturbo' badges. It's that kind of bling that gets people raising their little finger at you.

We only tested the Coupe, and I can tell you that the practicality perks on offer largely depend on where you're sitting.

Up front, you're spoiled for room in the two-door Coupe, with the two spacious seats separated by a sizeable centre console that's also home to two cupholders and a variety of cubbies, with extra bottle storage in each of the front doors. 

The back seat, though, is a little, or a lot, tighter, with come acrobatics required to even climb into it, given the Coupe only has two doors. The Sportback offers two more doors, which will surely make the process a little easier. 

The Coupe measures 4723mm in length, 1866mm in width and 1372mm in height, and will deliver a decent 410 litres in luggage space in the boot. The Sportback measures in at 4783mm, 1866mm and 1399mm, and boosts your luggage space to 465 litres.

Either vehicle has your tech needs sorted, with an abundance of USB and power outlets serving both front and backseat riders.

“Practicality” is about as relevant to this car as a code of ethics is to a drug dealer or a contract killer, because the SL63 buyer is hardly worried about cupholders and boot space. For what it's worth, there are four cupholders in the two-seater cabin (which might explain why owners aren't worried about their liquid carrying prospects) and a minimum boot space of 364 litres and a maximum - with roof up - of 504, which is actually not bad.

Cleverly, there's a little robot-operated luggage cover inside the deep boot that stops your gear from being crushed when the roof goes down.

There's also space in the long doors where you might secrete a bottle of wine that would get a NSW Premier fired if he thanks you for it, and a bin in the console to hide your phone.

It’s difficult to ponder the idea of value when a car is already approaching $400,000 at a rapid rate even before you start piling on the options. On the plus side, for a list price of $368,715 you do get an extremely long list of standard equipment.

The SL has always been completely unapologetic about its size.

Edited highlights include leather on almost every available surface, heated and cooled electric seats with a fan heater for your neck, a B&O stereo that will shatter the windscreen on request, aluminium trim that's real aluminium (mostly), Active Ride suspension, sat nav, dual-zone climate control, active cruise, LED headlights and a huge swag of safety gear.

The 12-speaker stereo also has DVD, limited smartphone integration via Mercedes' COMAND system, a seven-inch screen and, of course, Bluetooth.

Its a terrific engine, this - a twin-turbo 2.9-litre six-cylinder TFSI that will deliver 331kW at 5700rpm and 600Nm at 1900rpm, sending it thundering to all four wheels (because quattro) via an eight-speed tiptronic automatic.

That's enough, says Audi, to deliver a 0-100km/h sprint time of 3.9 seconds in the Coupe and the Sportback. Which is very, very quick.

The SL63 is powered by Mercedes’ increasingly famous V8, with two turbos along for the ride to add oomph and cut the car's famous consumption, at least slightly. The 5.5-litre unit produces a massive 430kW and a scarcely believable 900Nm of torque.

All of that heads rearward via a seven-speed dual-clutch transmission that helps sling the 4.6m, 1848kg machine to 100km/h in 4.1 seconds.

The RS5 Coupe will sip a claimed 9.4L/100km on the combined cycle, and emit a claimed 208g/km of Co2. It's fitted with a 58-litre fuel tank. 

The RS5 Coupe will the same 9.4L/100km, but emit 209g/km of Co2.

Much as is the case with the price, there's no real way to soften the blow here - the SL63 drinks like a footballer on Mad Monday, except it does it every day. The official combined cycle figure of 10.2L/100km is quite easy to double, as we did, averaging 21L/100km in mostly flowing suburban traffic. In the car’s defence, the accelerator pedal spent a good deal of time near the firewall.

The SL does have stop-start to help reduce its considerable environmental impact.

With our time behind the wheel limited to the RS5 Coupe, we can only really report on how the two-door feels on the road, but given the prodigious power on offer, it's unlikely the addition of two doors is going to make the Sportback any slower. 

In short, the RS5 is thunderously fast, collecting speed with utter nonchalance thanks to this thick and endless-feeling supply of power unleashed whenever you plant your right foot.

It makes even the most ham-fisted attempts at cornering feel fast as lightning, with the power flow able to make up for every slow entry and exit by simply piling on pace between bends. 

But that's what you expect from an RS model, right? So perhaps more impressive is the RS5's ability to transform back into a relatively sedate urban cruiser when the red mist subsides. The suspension is firm, especially over rough road surfaces, and you do need to be a little careful with the accelerator to avoid that lurching feeling at every green light, but driven calmly, it doubles as a everyday car quite nicely.

Like in the RS4, we did find the gearbox felt a little quick to change at pace, shifting up or down at strange moments on the way into or out of corners, but you can reclaim control via the paddle shifters.

There are a number of impressive things about the way the SL drives. Firstly, astronauts will be familiar with the galactic thrust of the V8. It seems endless, seamless and ready to sling the big coupe into the outer atmosphere. Few engines of any kind can match the relentless go on offer in the SL and much of the credit should go to the seven-speed twin-clutch transmission.

When you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops.

Containing a torque figure like the twin-turbo V8's requires a lot of electro-trickery to stop you from being launched off the road. The great thing about all that stuff is that it works unobtrusively and smoothly.

Mashing the carpet in an SL without traction control would create much sound and smoke but little forward progress, such is the twist on tap. The SL has a range of modes from full-nanny (which is meant to keep you on the slippery Alpine road you've chosen to get you to some Swiss ski resort) while turning the dial all the way around to Race loosens the bonds.

It's in this mode you'll have the most fun and it does seem that the intermediate settings are a bit of a waste of time. Race mode does little to diminish the amazing ride quality provided by the active suspension setup, but relaxes the reins on the huge rear tyres. Exiting roundabouts is suddenly a huge laugh, with the tail cheerfully breaking traction and the two-mode exhaust thundering in a most pleasant way.

Better still is that when you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops, with more on the way when you lift off. There's little to match the aural pleasures of a properly tuned V8 and Mercedes has resisted the temptation to quieten it down on the outside and generate a fake noise for the inside. Although that would be stupid in a convertible, if you think about it.

The SL63, despite its AMG badge, isn't about all-out handling, of course. The Ferrari California would definitely show it how it’s done on a winding country road. The SL is more about flow, building momentum and rarely shifting down to second gear. The monstrous torque is enough to keep things rolling but should you wish for a bit more of the exhaust bellow, second is there for the taking.

Hustling the big convertible feels wrong, not because it can't do it, but because it's not really what it's for. Having said that, it offers a kind of fun that nothing else on Earth will provide, not even a Bentley GTC.

With the roof up, the SL63 is a quiet place but not remarkably so. The huge sticky tyres do the cabin's hush no favours, with an annoying roar on a wider range of surfaces than you might expect.

Roof down, it's hardly a paragon of virtue. A lot of wind noise reaches the cabin, even well below the huge speeds the SL can reach. So if you want to talk, it's windows up you'll need to deploy the mesh screen that bridges the roll hoops.

Six airbags, ABS, stability and traction controls, blind-spot sensor, lane-departure warning, brake assist, active safety bonnet, lane-keep assist, driver attention detection, AEB.

Audi vehicles are covered by a three-year, unlimited-kilometre warranty, which is feeling more than a little underdone when compared to some competitors.

Services are due every 12 months or 15,000kms, and Audi allows you to pre-pay your service costs for the first five years, at a cost of $3,050.

The SL63 is covered by Mercedes' three-year/unlimited kilometre warranty. And, er, that's it.