the fact u pay 3 times more and aem has better filter, also is one piece and better built.
i installed a generic in my car and the battery is pushing against the tube since they didnt really make it right, its all good though(gonna relocate batt. anyways). At a certain RPM, thrs a whine to it, sounds like turbo.
defintely get an apexi filter though, saw test results against K&N, Blitz and the foam one, apexi is the best (lifetime durability and zero maintenence).