Definetly, you really want a good air flow, moving air. You could have a kick ass intake, but nothing going out, or awesome fans sucking air out, but nothing bringing it in fast, and youd still have alot of hot air. Whats even best is to create corridors in which the air can flow. Always make sure you clear up all the cables and organize them nice so that the air flows. But....if I were to have to choose one or the other, it would have to be exhaust. In fact, if you could somehow seal your computer, except for a very small entrance hole (me fantasizing again) you could create low pressure inside the case, hence lowering the temperature....that is...if you have a very solid case....and a very very strong fan.