Yes but if that were important we would be using true Diesel engines with #2 Diesel fuel not alcohol and nitro. But we want more power not efficiency, so we use a fuel that packs the power in with the expense of efficient. It's more effective, not more efficient. I suppose if one is doing 3D then the larger prop is more efficient in a hover. But not sure, both props would have the same thrust, the weight of the airplane. So the larger prop would be turning slower so less drag, but not sure which one would use more engine torque, though I suspect the smaller one would have less, but more power due to higher revs.