What is the BMW M6? A more focused and sporty M5? A rival for Porsche’s 911? Or, perhaps a working man’s Aston Martin? In some ways it could be all of those things, but equally none of them.

According to BMW, the £93,795 M6 competes against the £97,000 Jaguar XKR-S Coupé, £92,410 Maserati Gran Turismo S and £91,950 Aston Martin Vantage Coupé, but we could equally include the £106,820.00 Mercedes SL 63 AMG and £108,090 Audi R8 V10 Coupé.

But in my mind its closest rival has always been the M5. Fitted with an identical 4.4-litre twin-turbo V8 engine and powertrain, both models essentially achieve the same task, with equal aplomb and self-assured swagger. So why would anyone pay a £20,755 premium over the £73,040 M5?

What does the M6 offer compared to the M5?

Perhaps the best way to answer this question, until we actually drive both cars, is by looking at their specifications. As already mentioned, the M6 comes with the same 552 bhp 680 Nm (502 lb-ft) 4.4-litre V8 engine with M TwinPower Turbo technology, seven-speed M Double Clutch Transmission with Drivelogic and Active M Differential with fully variable distribution of drive between the rear wheels.

The Coupe will accelerate from 0–62 mph in 4.2 seconds, whilst the M6 Convertible needs a further 0.1 seconds (4.3 seconds) for the same increment (The M5 takes 4.4 seconds). Their 0–124 mph times are 12.6 and 13.1 seconds respectively (M5: 13.0 seconds), whilst both cars are credited with an electronically governed top speed of 155 mph, or 189 mph when fitted with the M Driver’s Package.

Spec M6 Coupe Difference
Dimensions (length, width, height) 4898 / 1899 / 1368 -12 mm shorter / +9mm wider / -88 mm lower
Wheelbase 2851 mm -113 mm shorter than M5
Rear track 1612 mm +30 mm wider than M5
Ground clearance 107 mm -10 mm lower than M5
Unladen weight (DIN) 1850 kg -20kg lighter than M5
Wheel Rims (front/rear) 9.5J x 19 LM / 10.5J x 19 LM 0.5″(12.5 mm) wider than M5
Steering ratio 1:13.1 27% quicker than M5

So, just from looking at the on-paper figures we can see that the M6 is lighter, shorter, lower and wider than the M5, with a quicker steering to take advantage of its shorter wheelbase.

Sounds good so far, but is that enough to justify its place as BMW’s top performance model?

The M styling cues and features

As you would expect, the new M6 is suitably attired with all the familiar M styling cues; a newly designed M kidney grille bearing an awkwardly positioned “M6” badge, hallmark M gills with integrated direction indicator bars, flared front wheel arches and the customary M twin exhausts positioned each side of the rear diffuser.

It’s clearly a much more aggressive car than the standard 6 Series, which goes some way in justifying the £22,000 premium over the 401 bhp 650i M Sport.

The M6 Convertible inherits the high-quality soft-top from the standard 6 Series, boasting its distinctive “fin” architecture, but the most notable difference between M6 Coupe and Convertible – apart from the extra £5,200 – is the additional 140 kg that its 552 bhp engine has to carry.

Performance, although reduced, is still bahn-stormingly quick, whilst fuel economy is knocked back a bit from the M6 Coupe’s 28.5 mpg to 27.4 mpg in the Convertible, but still an impressive 30 per cent improvement over the previous 5.0-litre V10-engined M6.

I understand why BMW chose to serve the convertible market, but I can’t help feel disappointed at the compromise it imposes on the dynamics and performance of BMW’s top M car.

What else is there to know?

The carbon fibre-reinforced plastic (CFRP) roof, introduced on its predecessor (codenamed E63), continues, but this time featuring a striking double-bubble contour that perfectly showcases the technical advances made by BMW’s Landshut production facility.

Other influences from BMW’s lightweight design strategy include aluminium for the doors and bonnet, thermoplastic for the front side panels and glass-fibre composite (SMC) for their boot lids (and roof cover in the case of the M6 Convertible).

For the first time on an M car, BMW are offering M carbon-ceramic brakes, further reducing un-sprung weight and providing fade-free performance even under heavy loads.

The diameter of the inner-vented and perforated brake disks increase by 10mm at the front to 410 mm, whilst the rears remain at 396 mm. The six-piston fixed-callipers are painted a special gold-coloured finish complete with M logo, replacing the standard dark blue metallic callipers used on steel discs.

The carbon-ceramic brakes are provided in conjunction with 20″ M light-alloy wheels and are made from a new type of carbon-fibre compound ceramic, but its not just stopping power that improves – a total of 19.4 kg is saved from the M6’s unsprung weight, further improving the M6’s ride quality and agility.

Technology

The biggest downside of being a near £100k car is that most customers expect every toy and gadget available in BMW’s armoury. That’s great for cruising on the motorway or in traffic, but not so good for a b-road blast or (heavens forbid) a gentle track-day dalliance.

But if gadgets ‘are’ your thing, you’ll not be disappointed with what you find in the new M6.

Adaptive LED Headlights are fitted as standard, as are an extensive range of BMW ConnectedDrive features including BMW Head-Up Display with M-specific information, High Beam Assistant, BMW Night Vision with pedestrian recognition, Lane Change Warning, Lane Departure Warning, rear-view camera, Surround View, Speed Limit Info, internet access, extended integration of smartphones and music players, Real-Time Traffic Information and apps for receiving web radio and using Facebook and Twitter.

To this already extensive list you can add; Comfort Access, active seats, heated steering wheel, doors with Soft Close Automatic function, Navigation system Professional and Bang & Olufsen High-End Surround Sound System with 16 loudspeakers in the M6 Coupe (12 speakers in the Convertible).

The M styling cues continue inside the M6 and include a newly developed M double-spoke leather steering wheel; M gear selector and car set-up controls on the centre console; exclusive M sports seats with integrated belt system (optional: M multifunction seats); Merino leather upholstery with extended features; exclusive carbon-fibre interior trim strips; illuminated door sill finishers with “M6” lettering; M-specific instrument cluster with black-panel technology; 2-zone automatic climate control with extended features and special ambient lighting.

Customers can choose from 1 non-metallic and 8 metallic shades for the exterior paintwork (including four exclusive M finishes), while the Convertible’s soft-top is available in Black and Beige, or Anthracite Silver effect as an option.

At £93,795 for the M6 Coupe and £98,995 for the Convertible, both cars will go on sale in the UK from 15 September 2012 after making their world premiere at next month’s Geneva Motor Show.

So, do all these features justify its £20k premium over the M5? Probably not. But then neither is the M6 just a 2-door coupe version of the M5. There’s all the extra style and image that only a coupe can offer, plus of course the inevitable peer association with Aston Martin’s Vantage.

It’s interesting to note Porsche’s 911 is no longer used for comparison, which is probably a reasonable move, given that it is 400kg+ lighter than the M6, but then maybe that’s where BMW are aiming for with the next M3..