they are both solid, great sweatfest circuit workouts. HSTA has more tall box leg presses which is fine with me. Really they are both very good. The production quality on HSTA doesn't seem as good, I'm not sure why, but that doesn't make any difference at all in the workout. HSTA has some different innovation moves that I have never seen before, like one armed dips with one leg raised for triceps and another exercise where you lean off the step and do a one armed raise for shoulders. Really, if these are the kind of workouts you are hoping for, tough circuit workouts with intense bouts of cardio and tough weight work that gets right into the muscles these are both fantastic. The only repetetive thing I can think of in them is that they both have hover squats which are grueling!!! yikes !!
The cardio in both the workouts is high intensity.
oh, HSC has a really fantastic, short but great, ab section at the end. HSTA does not have an ab section, but I think the length of the workouts taking out the abs is about the same.
I would say that I probably reach for HSC more than HSTA. I cannot tell you exactly why. They are both very very good. You could start with one and if you like it, definetly get the other.