Should I take the ACT?

I took the SAT without any preparation (not even the PSAT) and made a very poor score of 1500. I know 1500 is average, but my grades are much, much better and I know it doesn't truly represent my knowledge. I've taken a few SAT and ACT practice tests, but have actually the ACT. I score much higher on the ACT practice tests than the SAT. Should I study for the SAT and retake it or should I forget the SAT and just take the ACT?