Mamiya rb/rz backs film flatness of wind on verses motor powered backs.

Hi, Has anyone any info on the film flatness improvement (or not) onn using the mamiya motor powered backs verses the RB PRO S /Prob SD and RZ backs. Mamiya say there is improved film flatness of the Pro S and SD over the original Pro backs.
I know that the 220 fim provides better flatness, I an concerned with 120 film.
Regards,