Until recently, the SAT1 was considered the test of choice for college-bound students outside the Midwest. Now the two tests are considered equally valid, and either will be accepted by virtually all colleges and universities in the U.S., including Ivy League schools. (Harvey Mudd College, my son's alma mater, was the last holdout!)

The ACT (with sections on English, Reading, Math, and Science) strives to assess the knowledge you’ve acquired, meaning that the test focuses on subjects and skills taught in high school. The SAT1 (with sections on Critical Reading, Mathematics, and Writing) tries to assess “innate ability.” It does so using tricky and confusing phrasing that tap into test-taking skills (i.e., your performance under pressure and your ability to identify what’s being asked), and it relies more on advanced vocabulary and abstract reasoning.

The ACT appeals to many students because it is more explicitly achievement-based than the SAT1, has a science section, relies less on advanced vocabulary, and does not penalize errors. ACT also offers an optional Writing Section, which many colleges now require.

You should consider your strengths in comparison with the way subjects are tested by both tests. The ACT tests a broader range of subjects, but a weakness in one area is not necessarily as damaging on the ACT as on the SAT1. ACT questions are more straightforward than SAT1 items, which are often worded in an ambiguous way. In addition, you can more easily study actual subject matter to improve your ACT score.

You can get a rough idea of how the SAT1 and ACT scores compare by looking at an equilibration chart. For another perspective, you can look at a chart of percentile ranks for ACT scores and SAT1 scores.

You may want to consider taking both the ACT with Writing and the SAT1. That way, you can see how you do on each one, then either report the better score to colleges, or focus your test preparation efforts on one or the other for a retake. Some test preparation companies (Kaplan, Princeton Review) offer a free diagnostic test to help you figure out whether ACT or SAT1 is the better option for you.

Whether you end up taking the ACT with Writing or the SAT1, you still may have to take SAT2 Subject Tests. Two SAT2 tests are required by the University of California schools, and more selective private colleges and universities may also require (or recommend) SAT2 tests. Only a handful of schools, the most selective in the country, require 3 SAT2 tests (click for a list of SAT2 test requirements).

Fair Test: 
Test-Optional Colleges

ACT vs. SAT

Compass --
SAT2 Requirements

SAT2 - FAQ

The College Board

ACT Site

Kaplan's ACT / SAT Quiz Banks

Princeton Review's Word of the Day

Worksheet:
(ACT) or (SAT1 + SAT2)?

Smart Parent Critiques AP

Counselors' Corner: Should Students Take Both ACT and SAT?