I'm squarely in the STi camp. I think the 06-07 STi's look better than the Evo and they sound amazing. Others say I'm wrong and say the Evo IX is the more beautiful rally box and sounds better because it doesn't "sound like a blown up Honda".
I've had the pleasure of shooting and riding in both, so I'm going to post up my favorite shots of each and then let you pick your homologization special. Feel free to explain your choice as a comment. Let the battle continue!
STi:
Evo: