I have 1 15.3 and one 10.7 and the 15.3 is quieter by a good margin over the 10.7, but the 10.7 is still VERY quiet (and its 300GB!)
The Fujitsu MAS 36GB 15K I have is louder than both... but also faster so I'll accept that
for active cooling, I have a 80mm fan controlled by my CF633 based on the drive cage temp.