STS is definitely more comprehensive, fun and varied than P90X. I actually didn't really care for P90X and sold mine. It's the same handful of exercises done over and over and over. I developed tendonitis in my shoulder from all of the pushups. The leg workout is weak compared to anything Cathe has put out. The cardio mediocre (the KenpoX is actually embarrassingly bad - they like to shout for no apparent reason). I think STS is much better for the money.