At the moment I'm rather drawn to the xbox360, but I don't like the tacky white colour of it's exterior, and nor do I trust it's noise levels - I'm not sure if later revisions have fixed this.
The newer units have replaced the original DVD drive with a BenQ drive that is supposedly MUCH quieter. If you can wait until they release the 65nm version of the Xbox, I'm sure it'll be even quieter yet.
From what I've read though, with the new drive the unit is very quiet as is.