I would not cancel a card if you have had it for over 20 years. It sounds like you have two cards with an AF and identical benefits and you want to consolidate. Both Citi and Barclays have fee free AA cards you just need to call and request a product change. Then, you would want to use the card ever 6 months to keep it open. As others have mentioned, Citi offers more product change flexibility - like the custom cash card.

Still, I would wait until the time of the annual fee, and then ask if they have a retention offer to keep you around, this may be a good option to generate more miles or a statement credit an then you product change one of them next year.