In the end it will be which system is more fun to use and which costs less to use. I doubt either of these controllers will be a game changer, but I might be wrong. Can never gauge the effect of the casual gamer
The eyetoy already tracks a persons body movement to control a game, anything i have seen natal do can be replicated on the eyetoy with a bit less accuracy (MS copied sony? I believe sony was the first with the eyetoy concept)). The new controller for sony has been demoed at Gamescon and i believe they showed it being used well in games. Also the wii cannot do the same thing, it has limited sensitivity and accuracy; dont you wonder why so many times you just flick the controller one way or another for the wii? The motion plus helps but its still not as accurate.