They both very easy to break down, but the M3 cost even more to fix, buy the 2002 Skyline GTR vsepc or Ford Falcon FPV TYPHOON, they both faster than R8.
Audi S4, RS4, TT 3.2 and Benz AMG, Golf R32, Ford Focus, VW Golf R32, Jaguar Supercharge, Benz AMG are pretty fast too, you can get a real americian muscle like Fod Mastang for that price too. and it 不掉价.
Buy a review frist before you hand over your money.