The best OS layout would be windows since there is so much you can do on it and its layout doesn't suppress any of its capabilities. If the 360 blades, or any of the others, where used for the pc it would take ages to navigate through anything. You have to look at the question people then at the whole picture.
If the question was "What is the best OS for a console" then I would have to say XBMC lol then the 360 blades.