Although UCs are less SAT/ACT sensitive than most colleges (they tend to be more GPA sensitive, so your 4.0 unweighted GPA is definitely a good thing if you have a reasonable number of honors courses in your record), a higher score is better, especially if yours is on the lower end of the range (the ranges are shown at http://admission.universityofcalifornia.edu/freshman/profiles/index.html ).