depends if you want it to be quiet, or push a lot of air.
I have some Thermaltake's and some Cooler Master's.
if I stop the Thermaltake's, I have to put my ear right up to the cooler master ones to actually hear anything from them.
if I stop the cooler Master ones (not that I'd need to) I can still hear the buzzing of my Thermaltake ones. even when they're on the lowest speed.