I know the program at UCI is rigorous for bio, but I think in terms of premed opportunities it will present more than SB since research is a requirement for honors and the OC area has tons of hospitals for clinical experience.
Since your son is interested in CS Engineering, SB might be a better choice for him than it is for me, because I have heard good things about engineering at UCSB. He could also apply for honors in sophomore year, and if he has enough research experience already, he should apply for the College of Creative Studies program ASAP