Paul,
I don't claim to be a expert but I have done a lot of work with props on both the ECL and IC power. The main reason to use the "E" prop is load. The standard props are two to three times the blade thickness compared to the "E" blade (this is APC or other brands) and the hub is also much thicker. This is done to take the cyclic pounding of the IC engine. The thin "E" props use 30%+ less amps to turn the same rpm on our electric motors. That's a lot of extra battery you would need to haul around and likely would need a larger motor also, all adding more weight. The APC's are very hard to beat even the wood electric props don't match it's performance/amp draw. APC puts a lot of engineering into its props, that why cutting them down usually reduces the performance. This has been my experience, others may see it differently.
Best, DennisT