Here's something my friend Paul from The Princeton Review taught a group of students and parents at "College Night" last week.
Kids who like math much more than English tend to prefer the SAT. Kids who like English much more than math tend to prefer the ACT.
Why? As Paul put it,
"Because the SAT is 1/3 math. The ACT is 1/4 math. And if you don't understand what I just said, you should take the ACT."