Should I send my ACT, SAT, or both to colleges?

For SAT I only got 1490, but my superscore is 1540 so it may look good for colleges with score choice.
My ACT is 35 composite.
For colleges that superscore, would it be better to send both scores or just ACT?

Don’t mix up superscore with score choice. Even for schools that superscore SAT, 1540 is only equivalent to ACT 34 on Collegeboard’s concordance table. How are you section scores? Is there any section score in SAT appeared much better than the corresponding ACT section score? Are you going to take SAT2? You may just send in your ACT score. But if you are going to submit SAT2, you don’t need to hide your SAT scores.