Such different cars IMO!?... a Euro twin turbo 6 cylinder RWD BMW coupe that is essentially a 2 seater vs 2 rally-bred Jap 4 cylinder turbo AWD 4dr sedan's? I can understand your confusion between the STi and Evo... but the BMW is a completely different animal IMO?
I would think that your personal situation may dictate which way you should go between the 2 different styles... rather than purely which is the better car?
As John mentioned though, the options on the 135i really push up the price a lot... and I wouldn't be getting one without at least the brake and wheel upgrade... which is another $10k on top of the already $10k more price tag?
If I had the choice, in my situation... I'd be going for the STi 6spd sedan in white... but that's me!