Deciding whether the ACT or the SAT is better is something a lot of students struggle with. As far as universities go, there really is no preference for one over the other. So you should find the test that is better for you. Here's a good way to decide
– Take a practice ACT and a practice SAT
– Use the score concordance to find out which one you did better at
– Take that test
It’s really that simple for most people. For a few people who are applying to schools that need SAT subject tests, you may be better off taking the SAT.
You can also read these blog posts to see which test might be better suited to your situation.