The most important answer to the "SAT or ACT?" question is to check with your target schools about their requirements. If you have specific colleges in mind, find out from the high schools or your guidance which test the schools require or accept. Although the majority of colleges in the United States now accept both SAT or ACT test results, you'd better make sure about requirements of your target colleges.
If your target colleges accept both, think about which test you can better perform on.
The ACT is a more straightforward exam than the SAT, which can benefit students who are not naturally good test-takers. However, the ACT covers more advanced subjects than the SAT and also poses more of a time challenge for most students. Before you decide which test you can do better, do a few sample tests of both SAT and ACT and compare the results. Be sure that the sample tests cover all sections of the SAT and ACT.
One good reason for considering the ACT is that it may save you from having to take four SAT tests. Many competitive colleges now require applicants to take both the SAT I Reasoning Test and up to three SAT II Subject Tests. However, there are a number of schools including Boston College and Duke that do not require you to take SAT II tests if you take the ACT. So taking the ACT might save you hours of testing (and even more hours of preparation), and save your money.
Please note that these policies vary from school to school. There are a number of schools that require the SAT II regardless of their ACT or SAT I requirements. Be sure to do the research by yourself and make everything crystal clear before you make any decision over your test choice.
Even though most colleges now accept both SAT and ACT scores, familiarity is an important factor in the admissions process. If most students in your state take the SAT, for example, and you take the ACT, admission officers may wonder why.
Choosing the tests can be quite a completed process. So, spend time doing the research. Ask your high school teachers; talk to your classmates; think about your own particular situation. You keep spending time on this matter until you get everything clear for a smart choice. Your research time will be well worth it.