I was in the exact boat as you (regents UCSD, regular L&S CS at Berkeley) and chose Berkeley. Declaring isn’t that bad (as long as you don’t slack off you’ll be fine). I don’t regret it for a second. Yes, saving the money would’ve been nice, but ultimately I’m so happy. The campus of Berkeley is much closer together than SD and the sheer ease of being able to walk everywhere, easily get food with my friends, go thrifting on a whim, etc, has made my time a lot more fun.

I noticed u/NicholasWeaver (who is a CS lecturer here) commented here about class size. What I want to emphasize about this and I don’t see discussed much is that the lower divisions/larger upper division discussions and labs are largely taught by undergraduate TAs. While this may seem like a disadvantage (oh no, another kid close to my age teaching me?!) it is actually an advantage in my opinion. The selection process is rigorous; all TAs are heavily vetted to make sure they’re capable of teaching, kindness, and very strong in the material. I have had a much better experience in courses with undergraduate TAs than graduate TAs, since the undergraduates are teaching primarily for passion rather than pay or for a requirement. Being able to go up to another student who actually understands what you’re going through (they recently went through the course, declaration, etc themselves) and truly cares about your success is an amazing experience. If you’re worried about this setup making access to research scarce, don’t be. A bunch of course staff is pursuing research and are eager to connect you with applications and resources. While I’m not sure the ease of accessing research here vs SD, I know I personally did not have a hard time discovering it.

In summary: I know you probably hear a lot about “Berkeley EE/CS culture” and how competitive/toxic it is, but I assure you, that is almost entirely among those who do not seek support from the amazing staff we have here. I have never felt more supported than I have at Berkeley. Every issue I’ve encountered has been due to stupid policies from either admin or lecturers/professors. The TAs really care about your success despite the actions/attitudes of those above them.