The difference is with USC, it's true. Their talent level is astronomically better than the rest of the Pac-10. They're so much better than the rest of the conference at football, it's almost impossible to comprehend.
Then they should be winning most their games by 4 tds no matter how little they prepared. It doesn't happen. Cal has LOTS of guys SC wanted. Obviously the opposite is true, but they can only get so many guys on the field. They also get the benefit of the doubt when looking at players. OSU was recruiting a player and rivals had him as a 3 star. SC started recruiting him, the analyst immediately moved him to a 4 star. That sort of crap happens all the time.