OK, now I've tried both High Step workouts. I, by far, like High Step Challenge better. I really like the abs section in HSC while HST doesn't even have abs. I like the vairety of lower body work in HSC while most of the lower body work in HST was leg presses (leg presses BORE me after 3 or 4 cycles). The UB premix in HST would be worth adding on to other workouts, but that's about all I could recommend it for (IMO). I will do High Step Challenge regularly. It is just more fun and really gets the job done.