ORD is an AA hub, so the knock on effect will probably be the same regardless of whether they choose ORD or DFW. I doubt one flight would make that big a difference from AA's perspective. I agree it might provide an incentive for *alliance pax to switch, but doubt that it will really make that big an impact. I wish QF had stuck with the DFW option myself, it's a bigger hub with more options for onward connections.