Berkeley has graduate students, it's much bigger, class sizes are bigger, you don't get so much individualised attention.
Both Berkeley and Oberlin have Experimental College type things, Oberlin has ExCo, Berkeley has DeCal, but the courses offered are wider in Berkeley, because it's bigger! There's a "The Simpsons and Philosophy" course at Berkeley. There is / was a knife throwing ExCo at Oberlin. And a trapeze one!
Oberlin has the art rental program and Winter Term! And the conservatory! And me! :P
Plus, Berkeley rejected me. So Oberlin is better :P. An LAC is very different from a big university, the whole atmosphere is very different, which one would your friend like?
My kid, with the same choice, will probably choose Oberlin, primarily because of the conservatory, though I think the opportunity to work with professors directly in an undergraduate-focused, small setting sets Oberlin apart from Cal, where TA's and readers will be giving much of the individual attention and teaching writing. On the other hand, my older kid went to Cal (wouldn't think of Oberlin -- too cold) and loved it, even some of the huge classes, though the sciences there are brutal. He found lots of music opportunities -- a good orchestra, chamber music ensembles, a noon concert series, cut-rate tickets to visiting performances -- but Oberlin would seem a heaven for the musical kid. Cal also lacks the snootiness that might put someone off some other comparable choices (nobody says, "I go to school in San Francisco" as they do "I go to school in Boston" to avoid dropping an "H-bomb"), though Oberlin's history -- on the underground railroad, early admission of African-Americans and women -- is also very appealing and sets it apart. Because of the low cost and quality of the UC's it can be a hard decision, but you can't go wrong if your son is happy with his choice.