[votingprawn]

Even if you disregard motor efficiency (which I don't, as with a battery powered vehicle you treasure every Wh more than you treasure every gram of fuel!), propeller efficiency is also important. Ideally you want to match your motors power handling and efficiency with your propeller. A given propeller/motor combination will have a design point in terms of torque/airspeed/rpm, and operating significantly outside of that (e.g. having a power system designed for cruise but operating at zero airspeed) has penalties.

Unfortunately I'm traveling at the moment, but I spend a large amount of my time at work balancing propellers and motors and could provide some plots that might help explain this. One of the few things years of working in academia proved to me, is that I'm terrible at explaining things like this!