SAT and ACT, Which One?
The more important thing to realize is now that there's a new version of the SAT, the two tests are actually very similar. There are more similarities between the tests than differences. Here are a few main differences:
The essays are very different. The SAT essay asks you to read a persuasive essay and analyze it, and is 55 minutes long. The ACT asks you to take a stance on a position and argue in support of your position. Neither essay is more difficult than the other.
The ACT has stricter time restrictions. If you're going by "time per problem," the SAT is far more leniant than the ACT. So, if you're a fast-worker, then take advantage of that skill and consider the ACT. If you're a slower worker, than you may want to consider the SAT.
The math sections are formatted differently. The ACT allows calculators on the entire test, which is made up of nothing but multiple choice questions. The SAT has a no-calculator portion of the test as well as some fill in the blank questions (non-multiple choice).
The ACT has a science section. This section is more of a data anyalsis and reading section, but the topics are science related. If you really dislike science then you may want to consider the SAT.
Overall, you want to pick the test that you think gives you the biggest edge. Look deeply at a copy of both tests and really focus on your skills. Do they match up better with one test than the other? Do you have a better "feeling" about one test more than the other? Then take that one. If you're still stuck, then take a practice test of both and compare your results. You may be surprised what you find out.
Should you take both tests? If you're really stuck, then go ahead and prep for both and take both. There is quite a bit of carryover within the prep of both tests. However, it can be to your advantage to choose one test and devote all of your time preparing for that test.
Good luck with your studies! We'd love to help out here at the AAC, so let us know if you're interested in our prep services.