they are all the same in terms of performance. the pro is white and dose not come with a hard drive to save your games to whereas the elite is black and comes with a 120 gb harddrive and one month of gold membership. if you can find an arcade that comes with like 128 mb of memory or something and is white. its mostly just what color you want.
then you have some special edition elites what come with a free game promo, like the resident evil 5 box was red, halo 3 was camo green, mw2 is black with silver logos on it.