It depends on what you want to do. If I had no predisposition as to what I wanted to do a PhD in, I personally would choose Berkeley over Cal Tech any day of the week. However, if there's a certain advisor at Cal Tech that's a leader in the field you want to study, go to Cal Tech. For example, one of my interests is Compressed Sensing, and both Candes and Tropp (two big names in the field) are at Cal Tech in the ACM department. It all depends on what you want to do.
If you don't know what you want to do, pick Berkeley. There's just a heck of a lot more breadth there, pure and simple.