They are both excellent highly competitive schools and should not be taken lightly. Plus they have a lot better weather than Harvard.
“I’d be very happy at a school that lacks that kind of prestige such as UCSB” Sounds like you are scared because you are afraid you are going to be with all these super hard workers/smart kids. Relax, the admissions people thought you would do well. You sounds quite bright, now you have to focus on working a little harder