Hi guys! So I’m debating between taking the ACT and SAT and I don’t know what to take… I’m planning on applying to the top colleges (JHU, Berkeley, UCLA, Ivies, Stanford), and of course some mid tier colleges. Can I just take one- either the act or sat? Or should I take both? Do some colleges require you to submit both? Thank you so much for your help 
Doesn’t matter one bit which one you take. Take practice tests of both and see which one you do better on.
No schools require both. The trend of taking both tests is the result of high achieving students trying to gain an edge at top tier schools, but it isn’t necessary. You can get official practice tests for both on their sites. Try each one and see which you prefer. Each has its own pros and cons and it is best for you to decide for yourself.