You should buy NCAA 06!!!! Its backward compatible on both systems and has everything NCAA 10 lacks!!!! Better Atmosphere celebrations after big plays....Race for the Heisman which was 10 times better than the Next-gen version which only lets you control your created player....I believe it has create-a-team aka Team Builder as well....and the game looks and plays fantastic!!! You can't go wrong!!!!
If they patch in some better game modes and celebration animations and presentation into NCAA 10....then maybe it will be a decent purchase.
At least try the demo before making your opinion....