Should I submit the SAT or the ACT

If you can submit both, do so. Otherwise, it doesn't matter because you have a score of 99.9999% on 1 and 99.74% on the other.

None of the schools care which one you submit and it will have no bearing on your application because you met the standardized testing threshold.

Some schools like Harvard College treat a 33, 34,35,36 the same and others treat anything between 1500-1600 the same

Honestly in this situation, it is a coin toss, though if you could submit both it would never hurt. Both scores are excellent and exceed basically every college's threshold for a really good score. Research the schools you really want to go to and see what those who got accepted submitted; if one is significantly higher than the other, go with that. For example, I know at Stanford, 86% of the freshman class submitted SAT scores, but just 39% submitted ACT. If its closer to an even 50-50 split, a coin toss might be your best bet :)

definitely submit ACT (or both honestly) if you really need to choose. they are both impressive scores and i think sending both in will display your hard work and efforts that was put forth to the mastery of both tests. however, if you are inclined towards a STEM major, submit ACT to demonstrate your strength in science/math. if you are inclines towards a humanities/english/liberal arts/history major, submit SAT to display your strength in the english part of the test. hope this helps! also awesome job on these scores!