If you want to use the stock fan that comes with each of these, that's one thing. Probably something like:
fop38/thermoengine (close tie)
Bear in mind the 38cfm Delta fan is pretty much recognized as an obnoxious sounding fan.
Now, if you want to take just the heatsinks and put the best fan for the job on them, then things change a little.
I'd go with:
taisol with 92mm Sanyo Denki 55cfm.
thermoengine with 80mm Panaflo 47cfm
wbk with 80mm Panaflo 47cfm
fop with 80mm Panaflo 47cfm
I like the forged, large footprint of the taisol.
I like the radial fin idea behind the thermoengine
These are my own, honest opinions. Others will differ with me on these.