The way I see it, Natal's advantage is purely software based, its highly likely that as soon as Natal is released, Sony will be able to emulate alot of the tech employed by it, add in the PS3's up and coming 3D capabilities, we could get some really interesting games.
To say that Natal has any hardware advantage would be naive, looking at the Natal camera, there seems to be little or no difference between it and the PSeye, Sony have already said that they are capable of emulating this kind of thing though to a slightly lesser degree. http://www.product-reviews.net/2009/06/07/ps3s-playstation-eye-vs-xbox-360s-natal/
Its all going to be about precisuion vs depth of field, my criticism would be, how many people have enough space to make use of field depth?
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