P90X is mainly for weightlifting and building muscle mass, so it's pretty slow-paced. I like Insanity because it's more activity, more moving around, but it's more on the cardio side and mainly for toning your body. Going back to the injury discussion, I've seen my friend injure his back and have to go to the doctor's and physical therapy just from squats, so I've ruled both squats and deadlifts from my workouts. there are a lot of alternatives that work out the same muscle groups anyways. So far, I've only injured my hips with hip pointers, but that was because of my own mistake that I know of now.
@David - I didn't know you could do 1 arm chin-ups... You're stronger than me, man! Although I don't do chin-ups, I do pull-ups so I don't know how that would go with one arm.