WRX are fugly and they have a weak tranny. If you look around at msg boards, you'll read that if you add power to it, the stock tranny will die on you. Unlike the Celi where you just need a stronger clutch and that's it.
I'd go w/the Scion 'cuz it's got a 2.4L engine, so it's got plenty of room for improvement. You can go all TRD
and get 220ish hp and it'll be covered under warrenty, plus the TC is gonna have a huge aftermarket.