I chose UCSD over UCLA and Berkeley and was happy with the decision (and much happier than other friends I had who went to Berkeley and UCLA). I liked the campus better than the other two schools (it’s hard to beat being right by the beach!) and the weather, and UCSD had a good program in my desired major (biology). I knew many other students at UCSD who also chose the school over UCLA and Berkeley, so you won’t be alone there.
The only concern that there is that Berkeley’s and UCLA’s names hold more weight than UCSD’s name if you’re planning on going into a field that is very name-conscious or if you’re planning on living and working outside of California. That being said, from what my friends and family in the field have told me, computer science tends to be much more experience-based than name-based when it comes to schools (especially among students who are all from good schools). They care about what you can do, not necessarily where you got your degree. I’m not in computer science though, so YMMV.
I’d say go to a school where you will be happy. You can’t go wrong with any of the three. They are all good schools. You’ll do better and be more successful going to a school where you will be happy and will get interesting opportunities both inside and outside of your major.