The SAT was redesigned (beginning March 2016). The biggest change is that you are no longer penalized for incorrect answers. Therefore, if you don't know, GUESS! The organization of the sections and the scoring has also changed.
Look at the infographic below to compare the SAT and the ACT. Which one sounds like it will be more likely to display your strengths? OR when in doubt, take each and then re-take the test you were most comfortable with (or whichever you scored better on).