I did not apply to either school (well, I did to USC a while back then but did not fill out their secondary).
From my friends who interviewed at Pitt, they really liked the school but it is heavily represented by in-state residents because of the way Pitt and the state work together.
Anyway, I love southern cal's sunshine, although USC seems to be in a not-so-safe neighborhood (but probably not as bad as Temple or SUNY-downstate). I would go to USC.
Reputation-wise, yeah, Pitt is better but by how much? Unless you go for top 10 or 15, I would go with personal preference.