I beg to differ with your analysis sdsearch,
Bigger is not always better.
I've flown AY and can categorically state that, in its own 'little' way, it is superior to AA from the attitude of flight and ground personnel to availability of 'premium' seating on TATL flights. AY is more a Global airline than is AA which only achieves 'global' presence thru its partnerships with OW.
AS to mileage extensions......AY asks one to fly.....AA suggests you to eat your way to retention....