OK, i just tested my XBOX and the decibels is 68 - 69 dB (at 1m). So if you can live with that type of noise, then it won't be a problem for you.
Xbox is really bogus. It has this huge brick of a power supply plus it lacks an HD-DVD drive. PS3 is prolly better but by and large I think they both suck because they're both ego inflated by Howard Stringer (Sony) and Steve Ballmer (MS). Choose your master right there...