Oh yes, AA definitely has the shortest seat pitch. My knees are wedged into the seat in front of me. Have to try to spread my legs as much as I can to the edges of the seat in front of me, no way can I have them straight forward.
That being said, AA is a lot cheaper than United in terms of seat upgrades. And you can use miles to upgrade your seat on AA.
I haven't been in an airline lounge in close to 20 years, so I can't speak to those. But if you hate O'Hare, then I can only assume you have never had to connect at MSP or flown out of the new terminal in SLC. I've walked over a half mile going from one gate to another in MSP, and good luck finding a halfway decent restaurant along the way. Same with SLC, it's probably over a half-mile walk from check-in to the end of the new terminal and that includes the few people-movers they have.
If flying on United, O'Hare is super easy. After going through security you're right in concourse B, and then it's a short walk to the escalator and people movers to get to concourse C. Nothing is a long walk in the United concourses. And if you want some quick food to take on your flight, there's a food court in concourse C with a decent cheap Chinese restaurant. I could leave my place in Chicago ~2:10 before my flight, walk three blocks to the blue line, 40 minute light rail to the airport, 10 minute walk from the blue line stop to security, be through security and get some food with plenty of time to spare.