DOOD! Chill...UOP is a great school (despite the recent board results). USC has a national reputation, that could be part of it. Honestly, UOP doesn't quite have the name recognition outside of Cali that USC has. USC also has, by nature of its being a major health sciences institution, unique curricular offerings that other Cali schools may not have (besides UCSF). There are probably many other very good reasons (academic reputation, success on the CABOP exam, etc), but that's what I've got off the top of my head.
Besides...
UOP is in Stockton 😳
Just kidding, they're both great programs! Congratulations on getting into the UOP program, EarlyEditionDude!