Ever since the most recent SAT redesign, the SAT and ACT have been nearly identical tests. And colleges don't care which one you send, accepting the two interchangeably. It's a wasted opportunity not to prepare for both at once.
And because about half of our students get their best improvements on the SAT and the other half get their best improvements on the ACT, we always want our students to take both tests at least once after taking our course and not leave any points on the table.