I prefer Cathe's weight DVDs to her cardio DVDs, just because many of the cardio ones are still too difficult for me. And, with step, I get confused, the minute she turns her back to the camera, I am lost. My favorite cardio of hers is KPC and I can also do Basic Step.
Are you trying to gain muscle? Or lose fat? If you want to lose fat, you'll need to be doing some type of cardio, but it doesn't necessarily have to be DVDs if that's not what you prefer.