Alright, cool. Just so you know, graduate schools don’t really care about multiple majors or minors. I’m guessing your know this, and that your desire to take so many classes is due to your own ambition, rather than trying to appear favorably to grad schools. If so, you may want to consider just sticking to a single major, and taking classes outside of your major that interest you. Having multiple majors and minors will put a real strain on your schedule and make it really difficult to do activities outside of school, like research or internships, which are way more important to grad schools than multiple majors or minors. Taking so many classes will also make it difficult to get the grades you want, and confine you to taking specific classes that may not interest you, rather than exploring areas outside of your major(s). Odds are you aren’t going to like every class in a particular minor or major, even if it’s a field you are really interested in. I know this isn’t what you asked about, but I just thought I should tell you this because you will have a lot more opportunities to follow your own path if you don’t limit yourself to the guidelines of multiple majors or minors. Like you, I transferred wanting to do multiple majors, before learning about the disadvantages. It’s good that you’re so ambitious, but you might regret tying yourself down when you realize how many opportunities you miss in the process. Just a thought.
Back to your question. I don’t think grad schools really care about where you went for undergrad, so if that is your goal, the prestige of Berkeley probably won’t help you. It is somewhat competitive at Berkeley, but I suspect it’s not that much more difficult than Davis in terms of grading. I really don’t know though. Yes it does get hyped up because of its prestige, and in reality it’s probably not that much better of a school than Davis, although it does have more renowned faculty. Classes are large (as I’m sure they are at Davis) but professors hold regular office hours. If you attend them frequently and do well in your classes, you will be noticed by them. I wouldn’t let that deter you. Bear in mind I’m an English major, so I don’t have any experience with professors in your majors.
Overall, if prestige is at all important to you, Berkeley is a good bet. It will help you get jobs (you may end up wanting to work before going to grad school) and people will be impressed by it, although you may not care about that. If prestige really doesn’t matter to you and you get a better vibe from Davis, go to Davis. It’s a great school also, and yes it is much cheaper to live in that area than Berkeley. Berkeley is very urban, and it can get a bit hectic. I have never been to Davis, but it seems like it would be more slow paced and peaceful.
Oh, and you should repost this in the UC Transfer forum, because there are a lot of people there who can tell you the specific differences between the two schools.