I’ve visited most of the campuses multiple times. This is my quick opinion so take that for what it is worth.
SLO - Cute small town that is somewhat at odds with an expanding university. Very pretty location but the campus felt like a concrete jungle. Students seemed to use their dining swipes at on-campus fast food restaurants rather than at the dining hall. Students stated that dining hall wasn’t a social gathering area as it is at other schools. Lots of hiking and outdoor activities. Students seemed happy with their choice. Not as diverse as other colleges in CA.
Davis - I have a student who attends Davis. Definitely get off of the freeway and explore the campus and town. Flat campus that covers the largest footprint of any UC. Arboretum with a river and lots of greenery running through/around campus. Large grassy quads that serve as congregating spots. Surrounding college town partners with the campus creating a very close knit college community. I don’t remember the statistics but something like 80% of the city of Davis is affiliated with the university (students, faculty, staff, etc.). More bicycles than cars. Earthy, environmentally conscious students. UC Davis is more collaborative than competitive.
Irvine - Compact campus with buildings around the circumference of a central grassy park. University town center is across the street with Target and other chain stores and restaurants. In our experience, each college operates independently and it is more difficult to take courses in other departments than at other universities. Definitely confirm this for yourself rather than taking my word. Housing shortage this year and many sophomores who weren’t on campus last year weren’t told until July that they won’t have housing. Off campus housing is expensive. UCI is very quiet/empty on the weekends. Those that stay in town over weekends form close relationships but don’t expect a big social scene.
UCSD - Large spread out campus with 7 (soon to be 8) residential colleges. Lots of tall eucalyptus trees. We were disappointed that there was no real center of campus and not a lot (if any) grassy quads. Each residential college has different dorms and different GE requirements. You can state a preference but aren’t guaranteed your first choices. Strong STEM but definitely more competitive than collaborative. Some majors are impacted and they ask you to select a second choice major if your first choice is impacted. Regardless of selecting a major, some students are admitted as undeclared and asked to find a major after they enroll. Major housing shortage this year.
UCSB - 90% undergrad and 10% grad students so the focus is on undergrads. Three colleges - engineering, creative studies (very small and select) and L&S. Since almost every major is in L&S, it makes it easy to take any class you want and very easy to change majors. A biking campus on the beach. Neighboring college town of Isla Vista is a beachy rundown student community. While at Davis you would have professors, TAs, etc. living, shopping, dining in the same community as the students, at UCSB, Isla Vista is mostly undergrads and SB community college students. Beautiful location, close knit community but definitely more partying than at other campuses. Where UCI is quiet on weekends, UCSB has a lot happening on weekends.
USC - One of my children attends USC. Significantly more expensive than the UCs. Smaller class size than the UCs. Strong school spirit, large Greek system, many (but not all) very affluent students. USC has the Trojan Network of alumni which helps when finding internships and jobs, especially in CA. More customer service at USC than the UCs but email communication is worse than at the UCs. Emails are sent to some students and not others and departments (ex. housing, rec sports, hospitality, events) don’t seem to know what is happening in the other departments. Urban campus with beautiful brick buildings. Relatively large dorm rooms with no triples. Surrounding neighborhood is not safe. USC provides security within a certain zone and provides free Lyft in the evening.
Berkeley - Urban hilly campus. Buildings have an older east coast look. Very competitive, sometimes unhealthy, academic climate. Very large classes. If one doesn’t take the initiative, it is easy to feel like just another number at Cal. Major housing crises for several years. Some students go Greek just to ensure housing close to campus. Surrounding college town with a dirty grungy feel to it. A little farther out is not safe and similar to USC. A student needs to be aware of his/her surroundings. Lots of homeless in surrounding community.
UCLA - Beautiful urban campus with adjacent town of Westwood. Dorms have some of the best food in the nation. I believe two years of housing are still guaranteed (triples). Rigorous classes but not as cut throat or competitive as Cal. Lots of competition for internships, jobs, etc. but if one takes initiative, there are lots of opportunities. Lots of school spirit. Basketball is on campus but football games are played at the Rose Bowl in Pasadena which is approximately an hour away depending on traffic.
Stanford - Beautiful campus. Lots of biking. Surrounding community is expensive, affluent Palo Alto and not a college town. Most students live on campus or in a Greek house for all four years. If you have competitive stats, apply but make sure you evaluate it for more than the name before enrolling.
Additionally, we’ve toured LMU, SCU, USD and SDSU. We’ve visited UCM and CMC without tours.