Fist off, a 33 is a very good score somewhere around 98th percentile.
Take a timed full SAT practice test and see how you do? If the score is promising, then you can think about switching. Normally, students do better on one of the tests versus the other.
Also, in the future the ACT will allow testers to take individual sections of the ACT. So if you are doing “poorly” in one section (say Math is a 30 but in English, Reading, and Science are 35s) you can spend time studying the subject that is causing you trouble and only take that test. Check on the rules since its new for fall 2020 and beyond but it seems that most colleges in the future will let you superscore any section?
Lastly, you are only a rising Junior in the fall so you have a lot of time to prep and take the ACT over again. FYI - my D took the ACT 3x. The first two were fall of junior year and she got a 31, 32. She waited to take it again at the end of the summer as a rising junior and got a 34. I think the extra practice and waiting to take it the last time until she was really prepared helped her a lot.
Good luck to you.