Okay, so my sense of location is subjective, like everyone else's
. In particular, I think anywhere in CA is better than anywhere east of the Rookies
. I like that Davis is (relatively) close to the Sierras. I'm really pretty into hiking and outdoors stuff, so I like the idea that that is possible from Davis -- good areas for that are much less convenient around San Diego, which is mostly desert. I grew up in Oregon, so it's also a bit closer to what I'm familiar with. The beach is not what gets me excited about a place, but if beach and surfing really get you going, San Diego is the place to be, no doubt.
In terms of the actual campus, I had forgotten that the central valley is soooo flat. Also, I hear it gets ridiculously hot in the summer. UCSD has an advantage there, but at least Davis is accessible to bicycle transportation. I think that's pretty cool (the UCSD area did not work well on a bike).
Anyways, this is pretty mute at this point, as baring anything really bizarre on my visit, I'm far more likely to go to Berkeley than Davis. Or U of Washington, possibly. I would consider both to have better locations than Davis or San Diego.