AA: Better service, food and especially ground support if things go wrong; lie flat but angled, not horizontal, seats. (AA 767s to / from Europe will all undergo conversion to lie flats, but that CIP has only just begun.)
IB: Better hard product (lie flat horizontal seats) and wine; utter cr@p on the ground, especially in case of any irregularity or disruption.
As American Airlines and US Airways are still operating as distinct airlines, this question is being moved to the appropriate pre-merger airline forum.
Please note the sticky at the top of the consolidated thread which is titled Welcome to the New American Airlines Forum! PLEASE READ BEFORE POSTING. With all of the changes about, it is important to know where to post, and reading that thread before posting (as the title suggests
) will help get you in the right place.
~Moderator