Technically, all balls have a mass bias after drilling. A mass bias before drilling is present in asymmetrical balls. The intermediate differential will tell you how much of an influence the mass bias has in the ball.
Example. AMF Clutch has a intermediate diff of .008. That mass bias won't have much of an effect in the motion of the ball.
MoRich NSane LevRG has a intermediate diff of .035. MUCH stronger, therefore, much more influential in the motion of the ball. In my experience, it also means that you have to be much more accurate with the placement of the MB to achieve the desired ball reaction.
But, to simplify (It's hard for me to do that, lol), it's just another factor in laying out the ball. Asymmetrical have a tendency to hook/stop more than symmetrical, all things considered. Both are useful to have in your bag.
