Other things to consider:

AA has MRTC which is nice when comparing CO coach. CO has auto-elite upgrades that are no cost. AA requires 500-mile segment purchases. AA requires more points to upgrade to FC, i.e. 30k roundtrip to FC, CO is 20k. AA requires an expedite fee to upgrade using points if within a certain period of time, CO doesn't have this.

AA's 1MM deal (lifetime gold) can't be beat. AA also allows the gold/plt challenge, CO doesn't. I constantly take advantage of NWA promos for points. I use NWA points to upgrade my wife to CO FC. All of my experiences deal with domestic flights, no international as of yet. Many threads discuss CO's international upgrade issues. CO's BF seat is nice but difficult to get. My wife splits here travels between AA and CO and is usually able to maintain at least Silver on CO and Gold on AA. One last item to consider is if you fly CO and have an AMEX Plat card you can gain access to CO and NWA clubs. We pay for AA club access.