I have both and like CTX better, even though it is outdated. I like the ab work, and the weight work, which is endurance based feels much more thorough since its only bodypart/day.
4DS does use heavier weights, but I just don't feel like I get enough of a workout when I do it since you are doing 2 bodyparts in the same amount of time CTX does one. That being said, in 4DS, the set, the music, Cathe and the crew all look dynamite, so its much more pleasant to watch since its newer and more polished.
Lynn M.