All things being equal, you're generally better off with UC. The CSU system is a fine one, but they're not as nationally known as the UCs. When adcoms see an app from Cal State Northridge, it reads like a regional college. When they see one from UCLA, they know where you went to school.
Note my first sentence. This are not always equal. There are reasons for choosing CSU over UC for reasons of location. Some folks prefer CSUs due to smaller class sizes, but that's not really applicable to you, as the huge lecture hall classes are largely in the first two years.
Many folks from CSU do outstanding and get lots of admissions to great med schools. It won't hold you back. But like I said, all things being equal, UCs are more highly regarded.
Best of luck....