Which university should I transfer to UCSD or UCSB as a Psychology major?

Go to the school you will be most comfortable in. Grades will matter a ton when applying to graduate school so it is imperative that you choose the best place for you to focus and succeed. The reputation of the school wont matter when applying to graduate school but grades will matter A LOT. Hence, it is important to choose the school which you will feel comfortable in order to have good grades.