I moved from AA to UA, in part because of UA's very generous and flexible same day confirmed change policy, something that AA does not have.
AA and UA both do a pretty good job serving the smaller midwest cities, of course there are some airports that are only serviced by one carrier, but generally both have service via ORD.
For ORD-AZO, look into ORD-GRR as well when you can. Lots more options (GRR serviced via EWR,DEN,IAH,ORD,IAD on UA) and DCA (I think still),ORD,DFW,CLT,PHL on AA.
Something like SNA-DEN-GRR would be a good way to get there. The drive down to AZO is super easy, only about 45 minutes.