From psm3mag.com: "We've played a PS3, for a day, in a room, with it on a table in front of us. At no stage did anyone comment about the noise it made (ie, next to none). And a collegue put his hand behind the machine after it had been running for a few hours and felt warm air being quietly and safely extracted via a fan via the vents at the back of the machine. The surface of the machine remained at room temperature with a small portion at the back being 'warm'. Not hot - 'warm'.
So, the PSM3 independent verdict here is that - quote - "PS3 generates less heat and noise than the combination of 360 and powerbrick".