<p>Do you just need one or the other? Or do some colleges require you to take the SAT over ACT or vice versa?</p>
<p>Are there advantages to taking both or would it just be a waste of time?</p>
<p>It depends. Some people are wired to do better on one than the other. All colleges accept both equally. If you haven’t taken either, you should take both just to see which one you do better on.</p>
<p>Colleges only require one or the other, though there are nuances. For instance, at some, you don’t need SAT IIs if you submit the ACT, while you do if you send your SAT. At others you have to send SAT IIs with either. The only college I’m familiar with that requires a specific test is BYU, which at least used to require the ACT. </p>
<p>The take home point here is that you need to go to the college websites and read their requirements, there is no generality that can be made that will cover all schools.</p>