Davis definitely has the edge overall though: Washington Monthly
sorting by research davis is 27th vs 43 for irvine. Davis is also 42nd vs Irvine which is 46th, davis increased average gpa to 4.04 vs irvine which stayed at 4.02. Granted this stuff is relatively insignificant but you have to keep in mind you have 6.5k undergrad students per incoming freshmen class. A GPA difference of .01 is like introducing 260 more people with a 4.25 say. In UCD's case .02 GPA difference is the equivalent of having 520 more students with a 4.25 with everyone else having a 4.0 for ex.
More importantly: Stability, no, really. UC davis has a bunch more money in their endowment and partially due to their medical school they have dramatically more money being spent on research. 573 million v 300 million. With possible new procedures being introduced to not share the wealth generated by this research UCSB/UCI/UCR/UCSC/UCM will all be hit HARD while UCLA/UCSD/UCD/UCB (UCD actually beats berkeley in research expenditures) fair better.
Davis also has transfer applicants increase by 20% this year so while their overall acceptance rate went down to 45ish % or so the transfer student acceptance rate will be lower ( so you'll have a higher quality of transfer student which is nice).
UCI is definitely a good school, but davis does beat it for pre-med and likely will weather the financial storms the UC system faces better than UCI.