I've spent a little time on the USC campus, and all I can say is that the location is annoying -- a walled fortress in a sketchy part of town, which to me leaves something to be desired. Too much concrete. UCLA is supposedly much nicer in terms of location and grounds.
This doesn't change the fact that both are excellent schools, of course. Just seems like UCLA would have a nicer overall environment.
However, I believe that the "Old Boy Network" is the one thing that really works in USC's favor -- their primary placement advantage is supposedly the fact that they have a strong and loyal alumni network in L.A..