This thread pretty much says it already - http://www.m3post.com/forums/showthread.php?t=722287
I was going between an M3 and GT500. You can tell I went for the latter. It's cheaper to purchase, cheaper to maintain, far more power, much better aftermarket, and I wasn't planning on tracking it. Just wanted to enjoy street driving. I'm young and don't really need a super compliant ride, not that the GT500 isn't - It is very smooth. I'll worry about having plush BMW interior when I'm older. It still had all the technology I wanted (nav, bluetooth, media center). Both exhausts are to die for, in completely different ways.