As you are in ORD, AA is good second option. However, I think I would lean more towards skyteam for your second program as most of your trips are MRs and you are going to get better deals with someone who doesn't use ORD as a hub.

Going with Skyteam will give you more options for earning miles on more airlines and more sales (NW/CO/DL). NW/CO gives you free upgrades at low and mid tier for both programs that you would otherwise have to pay with stickers with AA, which may be a consideration. You have to watch out for COs low fares for EQM... but between NW and COs programs, I prefer NW's - more bonuses, better redemption, lots of bump opportunities for elites, and a great website. But AA has a good program and you really couldn't go wrong either way... I would focus more on what you hope to do with the miles and who has regular routes and sales that work for your schedule.