EasterBunny, we will have to disagree. Drives keep changing of course, and it's hard to keep up, so your mileage may differ.
I think the change in performance between AAM quiet and fast is generally pretty small and not something most people would notice. The change in noise level would definitely be noticed.
I believe today's WD drives are among the quietest and coolest running of any drives. I have some Samsung 120 GB and they are indeed quiet, but my Western Digitals are even quieter.
When formatting, defragging or running a drive diagnostic, I can hear the Samsung rumbling, if I try. My Western digitals in the same situation are totally quiet.
There are other bonuses as well to running the WDs quiet. According to storagereview.com or maybe it was silentpcreview, I don't remember, the WDs when set to quiet draw no more power when seeking than when not. This means their temperature doesn't increase when they are working hard. This, along with less stress on the head mechanism, should give longer drive life.