It depends on manufacturing costs. The whole point of designing a smaller foot print console is the reduction of components, reduction in die size of heat generating components, reduction in cooling system size, packaging materials, shipping cost, etc.
Essentially it enables reduction in production costs while still enabling a reduction in price at retail or maintaining higher profit margins per unit (or both).
In the case of the Xbox, it will allow MS to do a "relaunch" of the console along with Natal while still remaining the same hardware specs for developers.
It's a win-win situation.







