I don't have the toning ball kit, but I do have the cross train balance disk kit and like it a lot. I think the balance disk could probably be incorporated into some of the exercises you do with the sculpting bar. And the tubing from the cross train balance disk kit could be used with your stability ball in place of the resistance band to change up the resistance level from time to time. So I would pick the cross train balance disk kit over the toning ball kit because I think it offers more versatility.