There are two undergraduate admissions exam formats accepted by US universities:
You can also sit the ACT with Writing.
There are online resources comparing the two tests side by side, like this table from the Princeton Review.
Which test you take is up to your personal preference. You can take free sample tests on each exam’s website, and should play to your strengths. Please note that since September 2018, the ACT has been computer-based for international test-takers.
Check the exam and language proficiency requirements for each university to which you apply.
Test centre locations
Location might determine which test you take: