Which is Best For Biology and Science and For Economics
Best for you would be different for other posters.
Both have good programs for each major: Biological Sciences and Economics.
I suggest if you are focused on the academics to take a look at each majors course curriculum at both campuses and see if one campus fulfills your interest better than another.
https://basc.biology.ucdavis.edu/sites/g/files/dgvnsk3306/files/files/page/biosci_4yr_studyplan.pdf
https://ucdavis.pubs.curricunet.com/Catalog/ecn
http://catalogue.uci.edu/schoolofbiologicalsciences/#schoolrequirementstext
https://www.undergrad.socsci.uci.edu/files/degreeplans/econ_four.pdf