I say go for the Ferrari. The R8 is nice but like others have mentioned it will have basically the same performance as your M3.
Never driven a 360 but I did take a 430 for a spin and it was absolutely intoxicating. The sound of that v8 behind your ears is like non other. I'm sure the 360, or any Ferrari for that matter, would offer a similar experience. Plus would you rather say I drive a Ferrari or an Audi
