What kind of students would be better fit for the ACT in comparison to the SAT?
As a generalization, the ACT is easier but you have to work faster. And because of that, students who are willing to prep can often bring up their speed (and scores). Many students who are weaker in math find the ACT better because the problems themselves are easier. But as with all things, ymmv. If you can take a practice test of each, your preference may become clear.
The distinction used to be bigger: SAT was more of a test of innate abilities and ACT was more of a test of learned knowledge. However, that distinction is disappearing as SAT is moving in the direction of ACT.
Princeton Review has a pretty good comparison - Google Princetonreview.com Sat Act comparison. If you are good at science, the ACT science section can help bring your overall score up.
I’m pretty sure that Princeton Review offers a free hybrid sample test-- you take a little of one and a little of the other, and you can determine which is the better fit.
Of course, my guess is that it’s followed by a hard sell on taking their course, but if you can resist that it may be a good idea.