i always think you should get the cores out of the way first as they give the most stress, they're harder, and they're inevitable. in your later terms you'll be worrying pretty heavily about your thesis/big project, and if you have taken the core ones already, you can take fluff courses in your last terms if you want to make it easier to focus on the big thing.

still, you need enough of a mix of things you like to make the year worth finishing and so that college doesn't become drudgery, so i don't think one non-core elective will hurt you. good luck with your choice!