I've tried a yoga ball a few times before and found them to be too unstable / uncomfortable. I haven't compared since starting to use the Ariel 2.0 (for almost

I've tried a yoga ball a few times before and found them to be too unstable / uncomfortable. I haven't compared since starting to use the Ariel 2.0 (for almost 3 years now), but I will say that I enjoy the postures that I can adopt while sitting on what is essentially a fancy stool. A yoga ball wouldn't have the same height or allow me to rest my feet with my legs at the same angle. It's probably important to note that the active sitting chair requires a desk with an adjustable height so you can bring the desk up to the correct level for the chair.