What's important varies for different users with diferent needs.
Most people basically want quiet, efficient cooling, myself included. So I concern myself with decibel levels vs cooling efficiency. Another concern is ease of installation...
The only way to really get that info, is not by looking at specs(except dB levels), but by reading reviews of HSF combos in operation.
You can see in my sig what I went for....
I LOVE my Zalman and have bought another for my son's hot thunderbird 1.4GHz rig.
This one has a quiet 92mm fan and the thing looks like a work of art.