You asked a good question.
I would take them both. They would be good for you as some schools require one or the other or both. Also, talking them will help you with the process of test taking. If you do not do well in them, you can take them again. It would be good for you.
Here are some tips: http://college.usatoday.com/2016/05/09/act-test-prep/ http://college.usatoday.com/2015/08/29/sat-subject-test-tips/
How this helps!