It used to be a clear-cut situation: BMW M cars were fast around corners, and Mercedes AMG cars were fast in a straightline. But now the lines - and the curves - are blurred.

BMW also once dominated the luxury high-performance coupe sector with the mighty M3 while Mercedes-Benz kept the mantle of the best-selling high-performance sedan. But once the non-aggression treaty was broken, both German manufacturers jumped into each other's territory.

The result? BMW brought back the M3 sedan and now Mercedes has produced a two-door version of the C63 AMG.

The new Coupe that can go from 0-100km/h in a ballistic 4.3 seconds - faster than the sedan but also faster than the fastest M3, also the coupe, which takes 4.6 seconds.

Of course it's not all about numbers and acceleration times. We know from the success of the BMW M3 Coupe that there is more to a car than just being the fastest and that the C63 AMG coupe has a lot to prove in the ride and handling department to be a worthy contender for the M.

Before we charge into the coupe, it's important to analyse its sedan sibling. The C63 AMG sedan has always been a manic car; it can be truly brutal in every sense of the word and yet as comfortable as an E-Class saloon all in the space of five minutes.

It has so much power and torque that it's become a hit with tyre salesmen. Then there's the sound emitted from the quad-pipes that is almost deliberately tuned to scare little children and enrage environmentalists. It's like an enraged wolf, hungry to devour its next meal. If you're one of the few lucky C63 sedan owners, you know what we are talking about. It's about as fun as a practical sedan can be.

But the folks at Mercedes-Benz have taken the C63 AMG coupe to a different level. It's more grown up, more skilful and certainly more elegant in its road-hugging behaviour. It also seems to have worked out its differences with the rear tyres. Thankfully, though, it's still just as fun as the sedan.

Our C63 AMG Coupe test car came in obsidian black with AMG 19-inch matt-black alloys ($1980) and the highly recommended Performance Package ($14,900). With 358kW and 600Nm of torque (with the latter option), the 6.2-litre Mercedes-Benz AMG V8 will go down in history as one of the best naturally aspirated eight-cylinder engines of all time (along with the current M3's V8, to be fair). Its effortless power delivery and addictive sound is pure ecstasy in a world regulated by bureaucrats and red tape.

Behind the wheel the C63 is every bit a driver's car. It oozes enormous street presence and drives you in a never-ending pursuit of an open patch of road to unleash its might.

Coupled to Merc's new AMG Speedshift multi-clutch 7-speed transmission (MCT), the 6.2-litre V8 extracts its strength better than ever. Although not a dual-clutch transmission (DCT), the MCT does away with a traditional torque converter with lock-up clutch for a wet start-up clutch with the hydraulically operated multi-disc clutch located in an oil bath. Sound complicated? It is. But the result is rapid gearshifts, better acceleration and, believe it or not, better fuel economy.

In comfort mode the C63 behaves very much like a standard C-Class. If it wasn't for the AMG instrument cluster, AMG badging and the gorgeous sports seats, you could almost delude yourself into thinking it's a C250. Of course if you flatten the accelerator it instantly springs to life but otherwise the pedal response is very progressive and ideal for traffic or inner-city conditions. The V8 also tends to keep a low key in this mode to avoid unnecessary noise. Comfort mode is the only way you're ever going to come close to Mercedes-Benz's claimed 12.1L/100km fuel economy figure.

Turn the rotary dial in the centre instrument cluster to engage Sport and things begin to get a little more exciting. The accelerator pedal becomes sharper, engine revs get higher and gearshifts get 25 per cent faster. But the real party starts in Sport+, with an additional 25 per cent decrease in gearshift times (to 100 milliseconds) and the double-declutching function getting more ferocious on the downshifts. And even if you're legally deaf, you'll still hear the quad-exhaust pipes come to life with an adrenaline-charged note that will have the men in blue ducking for cover.

Driving around in Sport or Sport+ does come at a cost, though, as you'll become a regular at the local fuel station. Our average fuel economy for the week was at 18.2L/100km and that included long stints on the highway. If you're the type who is concerned about fuel usage, we suggest giving this one a miss (we hear Toyota is releasing a new Prius soon).

Although not exactly a pure race car, if you do happen to take it to a race track the manual mode is the way to go, giving you complete control over the gears thanks to the aluminium paddle shifters. Power delivery is exceptional in Sport+ and manual mode, ideal for when you absolutely must make that meeting (with the next corner).

Around the twisty stuff the C63 is a little different to its sedan sibling. It corners with even more control and precision and lacks the tendency to step out at the rear. You can indeed punch the throttle out of corners without the fear of God, but even so it's still the sort of car that requires enormous skill to master.

You can get in and go fast with relative ease but the more you drive it, the more you realise its potential is likely to be higher than your own ability (unless of course you're Lewis Hamilton, in which case your skill level will get you done by the Victorian police for hooning). It's not like the all-wheel-drive, RS-badged cars of Audi, where you simply point and shoot; this, like the BMW M3, requires your complete engagement to perform at its peak.

The high-performance AMG brakes get an upgrade as part of the performance package and are capable of pulling the C63 to a standstill in neck-breaking fashion. Despite hours of consistent 'spirited' driving, we experienced little to no brake fade. We did, however, get burnt by touching the aluminium pedals after the car was left in Brisbane's scorching sun.

The ultimate question still remains: Is the C 63 AMG coupe better than the M3 Coupe? We'll need a back-to-back comparison to find out, but it certainly feels on par.

Where the M3 feels slightly more agile and light, the C63 Coupe's frantic personality more than compensates. More importantly though, unlike the high-revving 4.0-litre V8 of the Beemer, which prefers to be revved into the stratosphere for maximum enjoyment (309kW at 8300rpm), the C63 achieves its optimum power level at 6800rpm.

There's simply just more grunt available from lower down the rev range, thanks to the Benz producing 50 per cent more torque (600Nm) than the M3.

The interior of the Benz is also superior to its direct rival. The two-tone black/red leather skin looks brilliant and there is an overwhelming sense of luxury inside.

BMW's iDrive is, however, more intuitive and simpler to use than the Comand system found in the Benz. Both support Internet browsing (tethered to your smartphone. Benz has no support for iPhones, but BMW does), Bluetooth telephone and digital audio streaming. Mercedes also offers an AMG instrument cluster with Racetimer, a system that measures lap times and displays an array of information on the state of the vehicle.

Although the current M3 is set for replacement in early 2014 - with a multi-turbo six-cylinder engine - it's still a great contender if you're after a pure performance coupe (particularly if you want a manual).

Otherwise the choice isn't necessarily still between the M3 Coupe and the C63 AMG Coupe; it's more a choice between the C63 AMG Coupe and sedan. We'd highly recommend you test drive both vehicles and go with the one that suits your driving style.

Check out the gallery for more photos of our black and red C63 AMG Coupe test cars.

- Car Advice