I agree with the above except wrt research: Your odds of doing meaningful research leading to being a 4th or 5th author on a publication are quite low as a UCB undergraduate, simply because there are so many stellar graduate students.
I assume that St Mary’s admitted you to the honors college giving you the best opportunities, access to the best professoes, etc. You can contact them and ask professors how likely it’d be for you to work in their lab and be 4th author on a publication (assuming you’ve done what is needed).
At Berkeley all your peers would be excellent. The intensity would be greater - some students crave that, others would rather have a more relaxed experience.
When it comes to med school, your odds of getting a med school-worthy GPA at St Marys are better, simply because you’ll be among the top students v. Average as at Berkeley and because grade deflation is greater at UCB.
So, really, the question is 1) how valuable is med school to you and 2) if you don’t end up attending med school like most would-be doctors, will you regret giving up UCBerkeley for St Mary’s?
2b) if you don’t get into med school, can you see yourself attending UCB for a Master’s degree or is UCB an undergraduate deal only for you? 2c) What sort of job would you do if you weren’t a doctor?