I have a PS3 launch unit and a newer Xbox 360 (Falcon). The PS3 is much quieter than the 360. The 360 (mine and my four friends that have one) is just plain loud. I know it's been said before, but when the DVD-ROM spins up, it sounds like a jet engine during takeoff. Fortunately, there's hard-drive install, so you don't have to listen to the disc while playing, but even just the fans are annoyingly loud. It's honestly not something I notice much while playing Halo or Gears multi-player, because there's just too much action going on most of the time, but in single player games, especially more thoughtful ones, like Prince of Persia or Fable or Mass Effect, I find the fan noise really annoying. It's so annoying to me, that I don't even like using the 360 for Netflix.
I've taken apart a 360 (my third broken one), and there's no way MS could have saved another penny on the design or construction. Everything inside is so cheap, the noise, the faulty optical drives, and the RROD aren't surprising. It's not like your typical nVidia or ATI reference board, made with high-quality components and over-designed cooling, assembled with precision. It's clear that MS prioritized cost-reduction over all else, and, frankly, along with promoting ease of development, it's a strategy that seems to have worked out well for them.
