Commuter policy at AA doesn't require any backup flights. AA jumpseat is on a reservation system. If you are the primary for the jumpseat it is yours (unless a fed shows up).
AA has 21 days vacation for new hires. I think UA tops out at a higher amount though. UA has the better min duty day, at AA it's 5:10 per duty period, so we have some 3 day trips that pay 10:20.
American doesn't have on airport reserve. Reserve callout for short call is "report promptly." I don't know where the upper limit of that is but 3 hours is common. AA has more retirements happening sooner and has hired less than United over the last few years. You will probably be better off seniority wise at AA. UA has the better contract but some of that will be offset by better seniority at AA. Contracts come and go, I wouldn't make a career decision based on who has the better contract right now.
AA does have profit sharing but it's much lower than United. I think it was about 3% of W2 earnings.