Advice for learning Statistics on Khan Academy

AP statistics will be the most difficult and comprehensive one out of the three. I have not tried the other two, but obviously, AP courses are more difficult than regular high school courses.

So your main criterion for what to choose is simply the desired difficulty level. Also, since skipping over things you've already learned is easy, make sure not to enter a state of analysis paralysis. Don't overthink it. Just pick the one that seems most appealing to you.