I think UCD will lead to more opportunities in the Bay Area with UCSB next and UCI leading to more opportunities in southern California.
I’ll try to describe my impressions of the different social scenes at the three schools. Full transparency, I have a child who is a student at UCD and I am an alum of UCSB and Cal.
UCD is a large biking campus with a surrounding college town. I think they say there are more bikes than cars in Davis. The students are friendly and the campus tends to be more collaborative than competitive. In general there is a more earthy, organic, bohemian vibe to UCD students.
UCSB is also a biking campus. It is 20 min north of the city of Santa Barbara. It’s college town, Isla Vista, is kind of a beachy student slum. Don’t get me wrong, students love IV but it isn’t the well manicured community adjacent to UCI. UCSB is 90% undergrad and 10% grad students. It has a beachy party social scene. I was much more focused and disciplined with my school work at UCSB compared to Cal because I knew there was always going to be something happening in the evening and on weekends.
UCI is a smaller walkable campus. It doesn’t have an adjacent college town and is pretty quiet on the weekends as a lot of locals go home. There is a bridge from campus to University Center with a lot of restaurants and retail stores. It is more commercial than the mom and pop type of businesses you will find at UCD or UCSB. https://www.shopirvinecompany.com/centers/irvine/university-center