Of the three that you showed, I would get the middle one as that is the style that I have used with good results. However, it doesn't matter which off those you use as they all work the same way and do the same thing. The difference is one engineer says "ours has a special shape to improve air movement", while another engineer says "the shape of our fan allows for less drag on the air flow", and the third engineer says "our fan is shaped for a more efficient air flow". The true difference between the shapes is probably so small that only an engineer can measure it.
Track you are wrong about the change of voltage with a speed controller, my friend. It doesn't hurt the ffans because the speed controller digitizes the ac voltage and then uses pulse width modulation (also known as digital frequency)to control the speed of the fan by literally turning it off and on dozens of times per second. Where normal reduction in voltage through a given resistance would result in a rise in current (Ohm's Law), which would damage the components over time, the use of pulse width modulation simulates a reduction in voltage over time, while at the same time cutting off the current fflow as well so that "Ohm's Law" is tricked to prevent damage.
The same is true for the digital HID ballasts. The bulbs are driven by high frequency rather than high voltage, so the ability to reduce the percentage of power in a "dimmable" ballast doesn't hurt the bulb because there is no rise in current with the drop in voltage.