In the manga GUNNM, the narrative arc where she plays motorball is distinct from the one where she gets the Berzerk (or URM) body. For personal reasons explained in the manga, she put the Berzerk body away and used a motorball dedicated body.
In the movie, it seems implied that with the support of Ido (and perhaps a bit of money) they crafted a Motorball dedicated body, distinct from the Berzerk body. While the Berzerk body is indeed powerful, they may have decided that it would be more efficient to craft a new body (and it would probably be easier to repair).
Take note that in the manga (even more than in the movie), cyborgs seems to change bodies very often (when they are destroyed or just want to adapt to a specific role).