I agree with Clare's comment about the music. If you want fun and variety (step and floor cardio, weights and bands), HSCh is the way to go. If you want a heart-pounding sweat-fest, then HSTA.
I like HSCh much better myself. For a more intense circuit workout, I reach for BootCamp more often than HSTA. However, HSTA has a better breakdown for it's premixes than HSCh (Upper body, Lower body, etc) and I use it for add-ons. The HSCh DVD has premixes for shorter workouts, but they are still in the circuit format and don't break out the exercises by body part.
Tough call!
Diane