Depends on where you go...or so I've seen from my interviews.
In my opinion, UOP has a really tight network of students (maybe since many come from UOP undergrad, where I go now) that are willing to help each other.
This maybe totally wrong, but I felt that UCSF and UCLA had less of a comradery (sp?) amongst it's student population, and that people were a little more competitive.
UCLA and UCSF are known for their competition for placement into a specialty program whereas UOP's dental school is strong clinically but lacks on the academic/research side. This probably has a role in the competitiveness of the school, since students at UOP are probably more willing to help each other, since most are planning for just a GP or AEGD/GPR, while those at UCLA/UCSF are trying to get into post-grad programs such as Ortho, Endo, OS, Perio...
Just my 2 cents.