Interesting points
@Claym, fun thought exercise no doubt.
I would like to point out that you sort of, perhaps inadvertently, gave one important clue as to why a pusher isn't as efficient as a "puller."
The fact that it generally makes more noise is an indicator that the prop is powering its way through dirty air. It is turning a small portion of the motors power into noise instead of thrust. Less thrust, less speed, all other things being equal.
It is certainty possible to build a pusher that can perform quite well but i dont think it will ever be more efficient than a similarly designed tractor.