Kiffin was forced to take chances on borderline character and academic guys in his year UT. These are the guys who eventually washed out. They looked great on paper and everyone in America wanted them, so its not like he signed a bunch of scrubs who never panned out for lack of physical talent.
At USC, he doesn't have to take the kinds of risks he did at UT. He has a better current product to sell, and to be honest, his heart is more into it in LA than it was in Knoxville. He was never at UT for the long haul, and in retrospect, it showed. He is passionate about USC, and naturally, you are a more effective salesman when you really believe in what you are selling.
He will always bring in superb talent at USC because of the recruiting base, tradition, and appeal of the SoCal lifestyle. The risks he took on guys like NuKeese, Darren Myles, Janzen, etc will be lessened at USC.