[serialk11r]

I think 1:1 is more efficient for any fixed gear strength as equal diameter gears have less sliding friction at the teeth for any given pitch. If the ratio is not 1, the smaller gear has to have a bigger angle between the teeth.

I think this matters a little less on hypoid gearing when the ring gear is driven, but when the ring gear is driving the pinion gear (e.g. engine braking) the friction is higher than with a bevel/helical gear. That's what I remember reading.

1:1 6th isn't popular because then your 1st has to be a very high ratio which is harder on the gears (gotta make it beefier).