There are no valid comparisons yet between the ACT and the new SAT so trying to figure out which may be better when both are high scores, is an exercise that leads to no valid conclusion. In that situation, you should send both.
If you google “new sat to act conversion”, a few websites will pop up with conversion charts. None of them have been made by College Board or ACT, but they could give you a rough estimate of the comparisons.
It appears ivysource is using the concordance tables between the old SAT, the ACT and the new SAT to convert from old SAT to new SAT. I doubt colleges will follow that model.
The concordance tables may not be perfect, but the percentile scores seem to agree with them. Your ACT composite is at 99.0642, and SAT composite is at 99.0273. You do seem to have a higher ACT, but at this point it’s really splitting hairs. I’d submit both and stop worrying about it.