I imagine if somebody had high constant winds, you could throw up any old sturdy wind-gen, and your batteries would stay topped off all the time. But, as I have been reading here, most of the discussion seems to be about getting some useable Watts more often from intermittent low winds.
After spending money and lots of effort to erect a wind-gen, it would be frustrating to find it isn't quite as productive as you had hoped. When staring at a wind-gen for hours and days, you would look for any way possible to increase efficiency even a tiny amount.
The experienced guys I've been reading always have the prop facing the wind (there are a few trailing wind-gens being experimented with), and if its on a draggy lattice tower , the prop is usually on a slender pipe stub to get it up and away from the towers wind turbulence.
If you could locate a web picture of a prop in a wind tunnel with smoke, you could see how far the turbulent air pocket extends behind it.
Here's another push-pull plane. The benefit was lower drag at top speed compared to a conventional twin-tractor engines, but worse fuel consumption at lower speeds (turbulence in the rear again) It was a short-range bomber-interceptor, fuel range was not the biggest concern.
http://en.wikipedia.org/wiki/Dornier_Do_335
I think this is still a useful discussion, because some people might only be allowed to have one wind-gen tower due to small property size and having neighbors near. If there's also limit on the allowable prop diameter, getting a few extra Watts from a second prop might be better than nothing...