The slim has better button responses
Dude the Slim all the way.. The phat has very little room for modding and its heavy. The slim has so much space for modding and after you take the UMD drive out its as light as air. I have three slims and one phat, when I use the phat and then pick up my beater (slim psp) I feel like I'm going to pitch it into the sky.
Slim,Faster motherboard plus more Flash 0 space, energy efficient perfect shape nd they're small to kuz like some dude said earlier there pocketsizeable kuz phat ones bring my pants down even wit belt (kuz i sag =) )