If you're talking about older e-bikes, and especially if you're talking about hub motor bikes, that makes perfect sense. But that's not the reality of the modern bike industry.
I could say that all lightbulbs at 40 watts and below are underpowered. I've used 40 watt incandescent lightbulbs before, and they were underpowered, but when I use 60 watt incandescent lightbulb they're great. So I recommend people not get 10 watt LED lightbulbs based on my experience with 40 and 60 watt lightbulbs in the past. See what I mean about how the power draw doesn't matter if it's not in context?
Like the example earlier of Shimano increasing both torque *and* range on the exact same battery with the upgrade from STePS 6000 to STePS 6100. It wasn't more wattage, the improvements came from drawing *less* wattage but doing more with each watt.
Computers are the same way, it's about the performance per watt, not increasing the watts the computer draws. Computers draw fewer watts than they used to, but do much more with each watt. If not for that, given how much more powerful they've become, you wouldn't be able to afford the power bill of owning a computer!
The future of e-bikes is drawing less power, but doing more with the power you draw. So I would ignore the wattage/voltage/amperage, and focus in on how much hill climbing power and how much range each e-bike offers. I'll take an efficient 36v bike that does a lot with each volt, over a 48v bike that uses power inefficiently. Hub motor e-bikes for years have focused on volts/watts/amps, but the future (at least with mid-drives) is to look at how many Nm of torque (measured at the crank) and the range you'll get with the battery you'll be using. Nothing's perfect, but that's the best indicator of the user experience of modern mid-drive e-bikes if all you've got is numbers to go by.
