I already have the DL AMEX, and am looking for a MC to supplement. I'll be spending ~$500/mo where my AMEX and Visa aren't accepted. From what I have read here and elsewhere on the web, the best offers that I have found are the 35K AA MC from Citi, and the 25K++ CO MC from Chase. Up until now I mostly fly DL, though have flown a little CO (~2000 mi) and no AA.

I have booked all of my travel through the end of the year and am scheduled to be making DL FO on 12/31. This would make me think that I would continue to try to fly DL next year (at least on paid flights). Looking at reward travel on both *A and AA, they seem to have similar availability on lower mileage flights (both seemingly better than DL). The main difference that I can see is the free checked bag on CO (which I really like on my DL card), but is this worth the intro mileage difference? I would really like for the 50K AA offer to be eligible on the MC.

Thanks in advance for all of your help!

Matt