Blowing Versus Sucking Fans ??

I tested my Cooler Master "Everest" IHC-H71 , see pic:

I changed the fans direction from blowing to sucking out air from HSF. The results? Not bad.... 3C degrees cooler. The fan's RPM increases too, from 5900RPM (blowing mode) to 6400RPM (sucking out mode). Loudness? hmmm.... I think at 6400rpm is slightly louder, but not much different. The 6000rpm fan is really loud and noisy, I couldn't stand it though so I switch back to Intel HSF with open casing.

i think when fans have less air to pull through (high pressure) they tend to increase in RPM. Sucking hot air out has always been used with major manufac. but it also depends on your set up as well and where the other case fans are placed.
If u seal up the space between the fan/heatsink it would probably help out even more.