I'm a graduate of UCSF, however, I've worked with many USC graduates who have had educations similar to mine and I'd have no issue with trusting their judgement on anything pharmaceutically related.
I think the reason you might perceive the difference is for a couple of reasons. First, for a long time, UCSF received more funding for research than USC did - I haven't checked this data in awhile, but that was the case historically. Now, the reason this has any bearing on education of pharmacy students is that you might be exposed to seeing research medications being used, depending on the state of clinical trials they are in. Or, if research is your bent, you'd be exposed to folks with lots of experience. There is a big PhD program there in pharmaceutical chemistry as well. But...if thats not your thing...then its no big deal.
Second, historically, UCSF has been a huge proponent of "clinical" involvement. In my day, that meant becoming involved in cutting edge clinical opportunities. However, over time, most pharmacy schools have come to appreciate the usefullness of clinical pharmacy in every practice setting, so going to one of the "few" schools which did this is no longer an issue.
Third, one of the deans of UCSF was actually an FDA commissioner - Jeri Goyan was FDA commissioner for a few years during the 70's. This is only important now because of the political connections which were cemented many, many years ago. The faculty there is extremely knowledgable not only in basic pharmaceutical sciences, but also in the politics of state & federal pharmaceutical issues. You won't work in a vacuum, so being able to manuever here is valuable.
As for clinical positions - you'll do fine with either school. For administrative positions, I think you need an administrative residency after you graduate from either school. No matter your decision - you will have a firm foundation from either school. A USC graduate can give you more insight into their program & their history. I'm very proud of my education, however, I'd never discount or diminish the education that USC pharmacists receive - all my professional (& personal, for that matter) encounters with their graduates have been positive and rewarding!
Best of luck ahead! You'll have a great experience with either school!