oil to a great extent is oil any will lube the bearings and gears as lr have used ep gear oils ,engine oil ,atf and mtf all worked welll if changed regular, the difference with gear boxes is the baulk ring to gear taper fit, and baulk rings design to remove enough oil to brake the gear but not remove all of it that you have dry metal to metal contact,different boxes often benefit by a particular oil,because gears and baulk rings can vary slightly not allways the same oil as each other,the biggest failing imo is not changing the oil regularly with older type oils that will be contamination and break down of oils capability, with the modern synthetics it will be contamination which does cause premature wear, a lot of box failures are down to not enough oil changes, which is very evident when you strip the boxes
Lads I have to say it’s a hard one to know which will cause the less wear over time for definite then? It doesn’t get that cold here in the sw of England btw fery