I also happen to like Peter taking out street crime... it's mostly what he does. Ultimate titles are supposed to be more true to reality and as such Peter would be spending most of his time in tights stopping petty crime, not duking it out with super-criminals (if only because the Ultimate universe hasn't had time to fill the streets with clowns in tights - though only a tiny few of his foes have been, most of his problems have been with super-soldier rejects - can't be a huge number of those). Furthermore this is teenage Spidey, he's still learning and as such the scope of his abilities is rather limited. Finally too much weirdness in so short a time (there's been darn near enough as it is) is really gonna screw the poor boy up well beyond his current hyper-tension.