Well, I think that by now we have (unintentionally) confused many readers.
My assumption is that in Dick's last example, his 29lb Extra uses a glow engine (not an electric motor) and the reasons for using a smaller prop deal with loading.
Without seeing Dick's data in a table format, it is easy to misinterpret what he wants us to see.
Michael's statements look true with the exception of motor efficiency. It only changes significantly with current draw.
Ideally, the e-power setup allows you to change the gear ratio as well. In higher end systems like the MaxCim brushless motors, the MEC gearbox needs only a simple pinion gear change to compensate for increased cell count or a prop change. In lower end systems like the GWS IPS and EPS series, you can either buy a different gearbox ratio to suit your needs or settle on the improvement that is gained from a cell count or prop change.
Dick is right about beginners needing a power system design that will not be damaged by use of full throttle. This is why I stated to "Use a setup that is best suited to your flying skills and habits".
Overall, the electric power systems have many ways to compensate for power and performance changes. Some if us don't consider it much fun unless we are pushing what we have to its limits. The subject has enough interest that I have a new column in Quiet Flyer based on this quest called "Hop Ups". My column premiered in the December issue and has already flooded me with e-mails. Everyone loves to hop things up!