The #1 reason I would choose AS over DL is their frequent flyer program.....there really is no comparison. With a revenue-based program like DL Skymiles, it would take a lot more $$ to earn the same elite status (and corresponding benefits) I currently enjoy on AS and I have no desire to pay more $$ for the same elite level. Even as a non-elite on AS, you'll earn more redeemable miles then you would on DL flights of the same fare class...the fact that Saver tickets on AS earn 100% EQMs/RDMs is amazing--DL, UA, and WN can't compete with that.