CFT,
Both are good, done in each direction. Also then the circle around the whole abdomen including around your back. Basically you are mimicing the main internal rotations of the tan tien, externally. Because of your instabile position on the ball your abdomen musculature will 'mirror' your movement. Then you get off the ball and repeat just the internal abdomen movement without any weights or arm motion in one of your 'standing' postures.
Good luck.