Math SAT vs. Math ACT
Many students consider the SAT and the ACT. Some take one or the other, some take both (some take both more than once). Hopefully the information in the table below will help you decide which exam is best for you. Of course, your decision should be made with the entire examination in mind, not just the math sections. You should discuss the decision with your parents and guidance counselor.
Although the content of the tests is similar, with math from middle school through precalculus, the ACT contains more Geometry. The SAT gives you more time per problem but has more multistep problems than the ACT and the SAT has a no calculator section. Many students find the ACT questions to be more straightforward, but the speed of the test is a challenge. Perhaps the best way to decide is to try practice tests for each and see how you do.
Another key difference is in score reporting. For the SAT, you can choose to send all of your SAT scores for all tests taken or the scores for a particular test date (the latter is called Score Choice). If you choose to send SAT scores for multiple tests, most colleges will consider your superscore (your best reading and best math across all tests). For the ACT you can choose to send scores for a particular test date or multiple test dates. There are some colleges that will superscore the ACT, but most will consider the ACT with the best overall average (called the composite score).
Quite a few colleges are test optional, meaning that they do not require standardized test scores. However if they do well on a standardized test, most students will send scores anyway.
SAT 
ACT 

Range of math needed 
Middle school through precalculus. Less Geometry.  Slightly wider (logarithms and matrices are included). 
Questions  No calculator section with 15 multiple choice and 5 gridins. Calculator section with 30 multiple choice and 8 gridins. 
One math section with 60 multiple choice problems and calculator allowed. 
Duration  No calculator section takes 25 minutes. Calculator section takes 55 minutes. 
One math section that takes 60 minutes. 
Time per question  No calculator section: 1.25 mins per question Calculator section: 1.45 mins per question 
1.0 mins per question 
Formulas supplied  Some  None, but formulas may be given in problems 
Diagrams  Drawn to scale unless indicated otherwise  Not drawn to scale 
Guessing penalty  No  No 
Calculator allowed  Yes  Not the TI89 or TINspire with CAS 