UCLA...Seems to be #1 in CA right now. They're big on research and unlike the past, when their students seemed to suffer from a limited patient pool, they have addressed that issue to some extent. Therefore, they seem to have picked up on the clinical aspect as well. However, in order to get into this school you need to have killer stats (We're talking 22+ DAT and 3.6+ GPA, and some impressive extra curricular work).
UCSF...Research seems to be their strong point. So, it's really the matter of whether or not you would like to earn a DDS/PhD degree. In addition, they have a DDS/MBA program (which UCLA doesn't have). So, if you're interested in that UCSF would be an ideal school.
USC...As you may know USC School of Dentistry has a different approach to dental education. In other words, they have a problem-based DDS program, which will give you a great clinical advantage compared to those students, who graduate from UC schools. However, I'm not sure how this approach will affect the performance of students on national board exams. Another factor to consider, before applying to USC, is their rediculously high tuition (I believe it's about ~350,000$ for 4 years). On the other hand, being part of the "Trojan Family" has its benefits after you graduate and you try to find a job!
Loma Linda...I personally don't like that school due to their criteria for admission. If you're not a christian, your chances of getting admission into that school is next to nothing.
Western University of Health Science...They've just started a dental program, so there isn't much information available out there. However, since they are a brand new school, I'm guessing they have some high-tech equipment and killer facilities. You might wanna research that for yourself.
In summary, I think all CA schools provide decent dental education. Otherwise, they wouldn't have been so competitive. So, at the end, in order to choose the right school you need to see what you want to pursuite, how much money you're willing to pay, and whether or not you want to stay close to home!
Good Luck👍