Would submitting both the ACT and SAT be more helpful than summitting only one of the tests to colleges?

I’m looking to raise both my ACT and SAT scores (or just one), and I was wondering if it would be helpful if I submitted only one test or both to colleges this fall. If I submitted one, I would submit the higher score, but would it be even more effective to summit both? Right now I have a 28 (ACT) and 1770 (SAT), but I’m hoping to raise one or both of them to a 30–32 and a 1900–2100. Essentially, one test or both? (Also, most of the colleges I’ll apply to will be in the Northeast.) Thanks.