UC vs transfer from a community college?

To be competitive for intercampus transfer and to minimize delays in graduation, you should complete the general education and major prerequisite requirements at your campus prior to the end of your sophomore year. The UC reciprocity agreement allows you to use the requirements from your campus to fulfill the requirements at the other UC campus. You may still successfully transfer without completing the requirements; however, you may be required to comply with the lower-division requirements at the destination UC after transfer and that could prolong your time to graduation.

You should also complete your major prerequisites in order to be competitive for admission consideration.

Berkeley generally discourages intercampus transfer. Applicants with compelling reason for needing the transfer and those who have exceptional academic records and/or leadership potentials are more likely to be considered for acceptance.

UCLA supposedly gives the same priority to intercampus transfer applicants as CA community college transfer applicants. But the admit rate of intercampus transfers tends to be lower compared to the admit rate of community college transfers.

Either seems fine, because in the end, you still are graduating from a good UC. The upside of community college is that you save several thousands in general education classes. You are going to do the same type of classes (mostly) during your first 2 years at UCSB anyways. But, community college have to apply for transfer, which has its own competition and risks.