We toured all of the UCs except for Riverside. These are just our perceptions so take them with a grain of salt. You really need to go and visit yourself to see which school is the right fit for you.
UCM - The campus is beautiful and modern with a lot of ongoing construction. You would think the Univ of CA would take some of their property surrounding the campus and add some social life for the students - pizza places, movie theaters, hang out spots, apartments, etc. Unfortunately, after 10 years, the college community around the school hasn’t developed. They do, however, have a shuttle to Yosemite.
UCSC - Unique campus in the redwoods (note: not on the beach). Students seemed to have a bohemian vibe to them. Has a unique college system without a central hub on campus. To us, the campus seemed dirty. It could be because the room where we sat for the admissions information presentation looked like it hadn’t been swept in months. It was first thing in the morning and the bathrooms were also dirty. It is sad to make an impression based off of that but the tour didn’t take us into any other buildings so first impressions stuck. We know lots of students who go there and love it. It is a huge hit for some and a huge miss for others.
UCI - Nice clean campus with large central green. Has a town center with restaurants, movie theater, Trader Joes, Target (coming soon), etc. Lots of social areas to study. They even have outdoor tables with solar umbrellas that provide energy to a charging station at the base of the umbrella. Multiple large parking structures across campus support the stereotype of a commuter school. Students who currently attend say that you need to force yourself to stay and not go home until Thanksgiving. Friendships develop between those that remain on campus over the weekends.
UCSB - Beautiful campus location. UCSB is a biking school. Isla Vista, the student community adjacent to the campus has kind of beachy, bohemian student slum type feel to it. The on campus dorm food is award winning. They were the first college campus to have a salad bar. Definitely more of a party school. There is always something going on. You are in charge of your own destiny. There are plenty of people who party and plenty that don’t. The university seems to be buying up a lot of the apartment complexes in Isla Vista to create more university housing.
UCD - Spread out campus with a central grassy hub where students hang out in between classes. The community around the campus is virtually all students or people associated with the university. Just like UCSB, UCD is a biking campus. Farmers markets once or twice a week. Farm fresh food is served in the dorms. They are finishing up building new dorms which should open in 2017.
UCSD - Very large spread out campus. Unique college system that you should look into before making your decision. Community around UCSD is very affluent, La Jolla. Lots of buses transporting students to and from campus. Vibe we got was very studious, very competitive.
UCLA - Beautiful campus with lots of school spirit. It can be very crowded and very competitive. Large Greek system. Has Westwood just off campus with restaurants, movie theaters, coffee houses etc. Very close to just about any social scene in LA.
UCB - East Coast look to the campus. There are no dorms on campus. Housing shortage is a big issue.There is talk about building student housing at People’s Park (homeless camp). Community around campus is pretty dirty. We got a bad vibe because admissions department treated students who were there for tours like herds of cattle. Lots of complaints in the Daily Cal about how crowded the school is and how difficult it is to get classes, reservations at RSF, etc.
Regarding majors, dorm size, etc., you should probably research that on the schools’ web sites.
I went to UCSB for undergrad and UCB for grad school. The schools couldn’t be more different yet I enjoyed them both.