Re: Mounting fan on Thermalright ultra 120
I really don't see how it can matter that much. The two are equivalent, surely, its exactly the same principle. If the air is pushing over the top, move the fan down a bit. If anything I would suggest pushing onto the fins, because:
a)the flow is more 'concentrated' (i.e. if its pulling the air can approach the fan from a wider set of angles)
b)fans create swirl. The HS vanes deflect the swirl into longitudinal motion (like a crude version of a jet engine stator). This is good because high airflow speed = high heat transfer (high nussult numbers)
c)no interaction between exhaust fan and swirl from intake fan, due to the HS acting as a flow straightener.
Basically I'm pointing to some reasons why you could pick, but it really shouldn't matter. I see absolutely no reason why people spend extra cash to use 2 fans (one on each side). It makes no sense to me.
EDIT: if you are really bothered, try both and see which one gives lower temps!