[aerohead]

In the past, Ricardo Engineering reported the highest efficiencies for CVT.
A 12-speed would have the equivalent efficiency.
We're up to 10-speeds presently.
BEVs with one-speed planetary gearsets have THE highest efficiencies in mpg-e.
Carmakers which claimed more efficiency for a 2-speed BEV transmission, and who produce a 2-speed BEV, have the lowest observed efficiencies of BEVs, although, perhaps not soley on account of gearing.
What's desirable is zero 'transient' loading of internal combustion engines, on account of a drift in the BSFC of the engine.
BEV's have, for all intents and purposes, a constant BSFC which is about 350% lower than an ICE.
Thermodynamically, ICE powerplants are presently the least efficient, and as motorists learn to count, are on their way out, by default.