New C63 out next year....likely to be 4WD with Twin Turbo V8 AMG purpose-built....going to be a rush for sure.
Definitely going to be an interesting head to head with the new M3.
From the pictures, I think the new M3 looks much better than the new Benz but will reserve final judgement for when I see them in real life.
At the moment I would go for a C63 over the M3. A c63 coupe with slightly wider PSS can keep up with a stock M3 no problem and is faster in a straight line of course - esp. with the P31 package.