I did campus visits at both schools a millions years ago when I was a senior. I also have friends who go to both schools and I've visited both of them inIrvine and in Isla Vista, the neighborhood that is right next to UCSB.
If you want to go to school and live in an off campus apartment in a neighborhood that is probably a clone of the suburban neighborhood from whence you came,if you like the idea of going to college in a town that rolls up its sidewalks at 9:00 pm, you want most of your off campus housing to mostly be filled withnon students and you want to shop and eat at chain establishments, go to UCI.
If you want a college town atmosphere, parties and neighborhoods that are populated by other students, go to UCSB.
Santa Barbara also has much, much better looking girls.
Irvine does have two advantages though, relative proximity to LA and warm beaches are only a few miles from where you'd be staying.
Both schools are about the same in terms of academics, which is what matters the most. If you can handle distractions go with SB but if you really want a calmplace to study and/or cannot handle distractions, go with Irvine.