Inefficiency is nonsense I'm my real experience, I ride with folk on Gen 5 Boschs, all down tuned to pretty much the same levels of power/torque similar fitness levels etc and we all run about the same battery drain in the real world, if anything mine is a couple percent better at times.
He's probably got an Amflow right? Which makes sense as my mates Amflow with the "first" gen motor is definitely louder than mine
I think at the end of the day, all the current "new" motors are pretty similar in real world use. I'd stop getting hung up on what the Internet says, find a bike you want and just buy it. Otherwise you'll be waiting til 2030 for a gen 5 Avinox and Gen 10 Bosch