So, Berkeley has the prestigious college of chemistry. But Irvine is a strong school too, and it sounds like it leaves you in better shape financially if you want to pursue graduate school. A degree from UCI with good grades will still leave you in a good place for graduate school apps.
Double majoring does not help you get into grad school. Major and get research experience in what you want to go to graduate school in: if you’re a biologist, don’t major in material science or vice versa.