Originally Posted by sdsearch

The "main" credit cards for UA and AA both give you some free checked bags. (How many depends on destination type.) Both these cards have a $95 annual fee, though you can easily find offers which waive the annual fee the first year, and at Citi you can often get the annual fee on AA cards credited in subsequent years too.

No credit card that I'm aware of (at least that costs any "reasonable" amount) gives you better seats. I believe you need actual elite status for that, and you can't get airline elite status on UA or AA from a credit card.

However, without status, you may be able to pay for better seats in advance at one airline but not at another. So if better seats are important to you, you may want to look into the advance seat purchase policies of each airline. (Just be aware of which seats are really better. A friend of mine made the mistake of paying extra for assigned seats when the airline wouldn't assign him seats otherwise, but he didn't know what he was doing and just paid extra for very ordinary seats, when there were extra-legroom seats on the plane. Don't trust the airline at the moment of purchase to clearly explain to you which seats are really better and why.)