They are both equally important, IMO. You don't have to memorize every single formula, but you should know the most basic and fundamental equations for each general subject covered, and be able to work with them and derive results QUICKLY. However, just as often you can solve a problem with some clever thinking and resourcefulness. The easiest thing to do (it sounds like you haven't yet) is to take one of the practice tests, and look at the answers for everything you got wrong, didn't answer, or weren't sure about at http://GREphysics.net
. You'll get a very good idea for what sort of knowledge you need to have for the test.