Why the comparison?
Because the timing couldn't be better. Mercedes-Benz has just introduced its second-generation CLS, while Audi has revealed its first attempt at a contender for the genre-busting Merc with its A7. They're both making bold claims about being sector-defining vehicles, while both like to think they're the greenest, most stylish and best to drive, too.
How are they similar?
Both chuck out convention and add a twist to an established genre of vehicles. Both claim to be 'four-door coupés', which in itself is a contradiction in terms. Think more rakish saloons than proper coupés. The CLS is the car that started the trend, while the A7 is Audi's attempt at getting a slice of the market for itself. Both claim to be sporting to drive while mixing grand touring credentials, though by both manufacturers' admissions they will be predominantly sold with diesel engines.
Both feature 3.0-litre, six-cylinder engines, the CLS confusingly badged 350 CDI, the Audi more conventional with its 3.0 TDI badge on the boot. The Mercedes-Benz gets 261bhp and 457lb.ft of torque, while the Audi gets 245bhp and 368lb.ft of torque. The Mercedes-Benz covers the 0-62mph sprint in 6.2 seconds, with the Audi taking just 0.1 seconds more.
On the environmental stakes there's not much in it either, with the CLS returning 47mpg and the Audi 47.1mpg, while the Audi's CO2 emissions figure is 158g/km and the Mercedes CLS 159g/km. Both achieve these impressive environmental figures in part by using stop-start systems, which cut off the engine while sitting idle.
The rakish lines in each do mean there are some compromises, mostly with regards to the passenger space. Head- and legroom in each isn't as generous as it is in their conventional saloon relatives.
Both ride well though, and despite their comfort there's some sporting appeal to the way they drive. The CLS feels slightly more involving, with its steering more alert and feelsome, but there's really not much in it on the road. In terms of safety equipment and driver assist systems both the Audi and Mercedes come will all the equipment you'd expect at this level.
How do they differ?
The numbers for the A7 and CLS are so close there's little in the way of tangible data to separate them. Changes then are relatively subjective, with the differences more down to your preferences and taste. Both largely borrow their interiors from other models in their range, but it's the Audi that arguably feels more special. There's nothing wrong with the interior of the CLS, it's just that Audi's interiors are a tough act to beat for usability and fit and finish.
The key difference is that the A7 is a hatchback compared to the saloon boot of the CLS. The A7 is also a quattro four-wheel drive model compared to the rear-wheel drive CLS. That brings more surefooted traction should you need it, but the CLS feels the more agile and interesting to drive regardless.
Both sell thanks to their looks, the CLS being a bit more extrovert in its style than the Audi. The A7 is arguably more elegant and less brash as a result, though some might find its looks a bit too restrained.
So which one would we have?
That's a tough call. Audi claims the A7 has some Avant (estate) practicality thanks to its large hatchback boot and certainly access is better than the CLS. Buyers are less likely to worry about boot space and its access though and concentrate more on style and driver appeal. On those counts the Mercedes-Benz beats its Audi rival. With the numbers being so close it's all down to pricing, which, as Mercedes-Benz hasn't released CLS prices for the UK as yet, makes a genuine conclusion difficult to make. If the money's right the CLS is the car we'd pick, but the Audi is incredibly close on all fronts.