UCLA gets more applications than Cal, in part because UCLA is in Southern California, the more populous part of the state. (There was a time when the San Francisco Bay Area had primacy, but that's *long* gone. (Cal alums sometimes call UCLA "The University of California for Lower Achievers," but that is totally wrong. Cal still has the more prestigious graduate schools, and Cal's law school is more prestigious than UCLA's (on the other hand, Cal has no medical school --one has to go across the river to San Francisco fro that), but I am not at all sure there is a good reason to prefer Cal to UCLA as an undergraduate school. That hurts because I am a double graduate of Cal.
Cal has a branding problem as well: is the institution "Cal" or is it "Berkeley?"" Cal sports fans dislike being associated with "Berkeley,"(a name they associated with radicalism) but most outsiders know the institution as "Berkeley." The place's official name is the University of California, Berkeley, but it's not clear what the short name is. I never heard the term "Cal" when I was a student ages ago, and "California" was used only for the sports teams. The institution has a task force working on this. For the moment, the branding problem prevents Cal, or whatever its name is, from getting the full benefit of whatever sports success it has (say, in crew or swimming or rugby).
Speaking of branding -- when Franklin Murphy took over in the 1950s as Chancellor of "the University of California, Los Angeles," he had to put a lot of energy into persuading the switchboard operators to use "UCLA" when answering phone calls from the outside world. Clearly he succeeded! I remember as a kid inthe late 50s looking at a publication advertising future featured college football games and "UCLA" was listed as the opponent in one of them.