It isn't so much as a preference to what you use. It is what the manufacturer recommends. The old Peerless gear transaxles used bentonite in most cases but there was a few that used 75W90, and the Peerless hydrostats used 10W30. Hydrogear uses 20W50, but Tuff-Torq recomments synthetic 5W50. The old rear engine snappers used 00 grease.
But then companies like JD will recommend Hy-Gard Low-Vis in their transmisisons which are Tuff-Torq in their mowers. Or in the case of Kubota front axles on compact tractors they recommend either 75W90 or Super UDT.
