I eschew the WD Caviar Black because it's always on and quite a heater. Same for Caviar Blue. On the plus side, I've had two WD Caviar Greens on my 722 and 612s for years and they work like a champ. They aggressively spin down for the 99% of the time the receiver doesn't need them. But when it does, they spin up again and all is well.