The only difference between commuting on AE vs AA is the Eagle guy will get the cockpit JS ahead of an AA guy on Eagle, and the AA guy will get the JS ahead of the Eagle guy on AA. JS is based on seniority, all other non-reving is (essentially) based on check in time - first come first served.
The time you spend on reserve in ORD will be negligible, in DFW significant. It is exponentially harder to commute while on reserve. I would hazzard a guess that you will prefer ORD by a wide margin. Unless you really,
really want to fly a SAAB.