Moderator, this same question has been asked in the UA forum, here

To the OP, please check this comparison United Airlines * American Airlines

flyastrojets , I find the Jan.25/2003 JSD thread you suggested no longer referenceable due to its many mistakes for not being updated, e.g.:

a) UA MP won't qualify based on fare class - False
b) AA Platinum Desk is better than UA's Premier Executive - What's AA platinum Desk - False
c) AA gives bag tags for PLT - False
d) AA will block center seats - False
e) and the list goes on and on

thus not usable anymore as a reference - or the reader might get so many wrong info that it'd be useless.