They're very different, as their physical structures are different. R2 is easier to control because he's not a ball (BB8 takes some practice, but is a lot of fun). R2 has lights and sounds that come from his body. BB8's sounds come from the app. If the goal is to have remote control droids, then I'd say choose your favorite droid. If you want more functionality, choose R2. But BB8 is very novel and fun and crosses different surface types more easily.