I got into both schools. UCSB as a political science major and UCSD as an International Business major. Im definitely more interested in business but UCSB doesn’t have a business program. I plan on going into law so my major doesn’t matter too much but I want something reliable to fall back on if law doesn’t work out as planned.
According to US News UCSB is a better school (they actually rate UCSD fairly low) and according to Forbes UCSD is a little bit better. I always thought that UCSD was a much better school academically, though after a lot of research it seems like UCSB is a better school now. I’m not really sure how they come up with “whats a better school” but yeah.
Here are my pros and cons: (lmk if I’m missing any)
UC Santa Barbra
pros: Right by the beach, have friends there, the school is much more fun (I’m very social), closer to home, weather
cons: doesn’t have my preferred major, small dorms
UC San Diego
pros: preferred major, awesome teachers
cons: barely any school spirit (no parties, ppl arent social), overly large campus
@Elilinden Hi! UCSB alum here. It sounds like your heart is with UCSB, and I think trusting your gut it is important. Take a look at the Global Studies major at UCSB (it’s not an impacted major so easy to switch). Some amazing professors in the program- I loved it! Several of my colleagues from the major went on to law school, so it’s worth a look. Could also be easy to double with Poli Sci, as there’s some overlap. Yep- the dorms are small, but it’s just a year and a fun way to meet people. Good luck! 
Forget the rankings - they are both great schools and the rankings emphasize different things that may or may not matter to you personally. So go with what does matter to you - the program/ major available and the social life. It sounds like right now UCSD wins for the first and UCSB for the 2nd. So maybe look at what the previous poster suggested as far as an alternate major at UCSB or poke around a little more and see if there are any more that grab your attention. And poke around a little more about investigating the social life at UCSD. Yes, it doesn’t have the same overall reputation as UCSB but I’m sure there is fun to be had… see if you can figure out where and how hard it is to find and whether it would be enough.
Just one person’s experience but D20 (future business major) did a summer program last year at UCSD and her PhD candidate instructor told her if she wants to study Business in college don’t come to UCSD. They are known primarily for their STEM programs and the campus seems very sterile (think gray, geometric boxes, and not planned out correctly). UCSB would seem to be the better choice for a future lawyer and someone who cares about an active social life while in college. UCSB also has 7K less undergrads.