Naturally, I'd have to recommend the Nissan.

I will say this much though -- you will tire of the NVH, especially since you've driven German cars for the last several years. The Nismo is quick and the rev-matched downshifts are a hoot. It's just the engine transmits so much vibration at high RPM. Oh, and you lose leather in the Nismo. I think a regular 370 with all the premium goodies would suit you better. Synchro-Match is available in all 6-speed 370's...

The interior is much better in the Benz. I'd throw a few more $$$ into the mix and get the C-Coupe, with the next motor up from the 250. Even if you don't 'race' the 250 is an over-burdened motor in that car.