These are 2 good schools. It looks like you’ve already given this a good deal of thought and have listed many of the salient differences.
I’d disagree with the “hard to get classes” part. UCSB has a 3-pass system for enrolling where at first you can only sign up for 3 classes to try to distribute them more equitably. As you rise in class standing your registration time becomes earlier in each pass. If you enroll in Honors you can get priority registration. Overall you may not get everything you want every quarter, but you’re not going to be shut out either.
Since housing has been brought up, UCSB has a program that guarantees 4 years of housing at https://www.housing.ucsb.edu/residence-halls/2-2-program but it is common for students to live in the dorms for a year or two and then either find an apartment in Isla Vista with friends or find a room with a friend in an apartment already rented but looking for new roomates since some people graduated. Some apartments overlooking the ocean stay in the same family for a decade with brothers and sisters passing thru and other roomates brought in to fill it up!
Not only is UCSB on the beach but it is one of the few college towns in CA. Your friends are going to be a walk or short bike ride away, the area right around campus is student dominated. Santa Clara is in the heart of the San Jose area so you won’t have that same “away at college” feeling, but from what I hear from friends who went there is that it is a close-knit school and there is a sense of commonality no matter what your major since they have a University Core Curriculum that is tighter than it is at a UC.