[Ryland]

The only flaw I found in your writing was "All three blades experience the same apparent wind speed and direction all the time." this might appear to be true but it's not, because when a blade is at the top if it's rotation it's higher then the blade below it at that is at the bottom of it's rotation, I don't have the chart in front of me, but if my memory is correct a 12 foot blade in a 12mph average wind speed on a 120 foot tower is going to have closer to 11mph wind speed on the tip of the lowest blade and that 1mph diffidence at those speeds is going to translate to nearly half the energy hitting that lower blade, because the energy in wind is cubed as speed increases.
As for the city lot question, most city lots a tower has to be the hight of the tower from the property line unless your neighbors give you and ok, so why not put it on a short tower? turbulence, I've seen the airometer spin backwards at my parents house because of the turbulence next to the buildings as it's only 30 feet up, this is a little 3 cup wind speed indicator, so for it to spin backwards the wind has to swirl around it perfectly, granted this has only happened a few times that I have seen, but it's because of the buildings, for this reason the most basic rule is no less then 30 feet higher then anything within 200 feet and ideally 50 feet higher then anything within 200 feet, as any ground clutter causes drag, there are charts out there comparing wind speed in a field with knee high grass, to a golf course mowed lawn, at 100 feet up! that is why it's always best to go with the tallest tower you can get and why roof top mounts are a bad bad bad idea, that and you are attaching a spinning moving wind catching device to your roof.