M3's are quality cars and they look good...
BUT IMO
Too expensive for what they have to offer, cant mod them unless you want to spend some serious money on a car that's over-priced to begin with, and they sound like crap with an aftermarket exhaust(sorry).
The Z06 may not have the same quality as the M3, but it will cost you less, its faster, takes well to mods which wont cost you an arm and 3 legs.