If I were Chip Kelly, i'd go with UCLA.
He knows the West Coast and has deep ties there already. The Pac-12 is wide open as a conference -- USC and Washington are solid, but nowhere near Alabama's level. And UCLA is a good program with good tradition and has the potential to be a contender with the right coach.
I personally would pick Florida. Better conference. Football is king in the state of Florida. And Florida fans are begging for the return of high-powered offense. Plus, while you're competing with FSU and Miami for in-state talent, you don't have to deal with a cross-town rival like USC.
I think Kelly will pick UCLA, and Florida will go hard for Scott Frost. I actually think Frost will turn down UF and go to Nebraska, and UF will then go after Dan Mullen which will prove to be an underwhelming hire in the eyes of UF fans.