I got quite a few grants and scholarships that I didn't even apply for at my UC school, comparable to scholarships I was offered at privates.
Going to a UC definitely makes it easier to match back into California. Of course, tons of people match back from other places, but being in California and associated with the system will make it easier to get into all the great UC residency programs. Also, California has the better weather, regardless of the storm that went pass Northern California last week. My reason for choosing a UC also included wanting to be close to family and friends. If that is a consideration, then there is really no point in going to a out of state private, though USC, Stanford, and Loma Linda aren't bad choices either.