Confusion! ACT or SAT?

Im currently an uprising senior that is just now taking the ACT. I haven't taken any official test yet but have done a fair share of practice tests. Recently I have dabbled in the SAT prep since I saw someone post that it helped them tremendously when taking the ACT since the SAT is presumably harder. So I go to do a bit of the SAT prep on Khan Academy and found that the Reading and Writing portion is a lot easier than the ACT's. Unfortunately, my math skills aren't up to par with my Reading and Writing skills, which puts me in a pickle. Do I keep taking the ACT over and over again or give myself a good shot at the SAT? I feel as though there is more, and better, prep for the SAT which could help with the studying portion? (I also keep falling short with time in the ACT timed practice tests because I am also a slow test-taker.) Please let me know what y'all think! Thanks xo