[suicideneil]

Pro diff has a lower gear ratio meaning you need to gear much higher at the spur/pinion to get the desired speed. The Pro also have spiral cut gears that load the bearings more, causing them to fail more often; the standard buggy diffs ( non-pro) are the ones everyone uses including myself- they last forever, though there are actually better ones out there that have metal inserts inside the diff cup, to reinforce the spider gear shafts. I forget the exact model they come from though at present...