the ball berring means, that when u are say 5600 rpm (ie highish rpm) that when u put flat again, the bb unit can catch up quicker then the bush unit. ie less lag. other then that, some bush units have put out more power then bb.
i just got a 180sx and their is a switch on the right side of the steering wheel next to the pop-up light button here is a pic to have a look at.. 56k warning, pic is quite big
thanks in advance