One HUGE pro is that Expedia allows a "risk-free" 24 hr cancellation even when a booking is made within seven days of travel, which is no longer possible on AA. Do note that if you're attempting to cancel on the day of departure, easy online cancellation cannot be performed through Expedia's website after you've checked in for your flight.

AA does still allow changes to be made within 24 hours when booking within those final 7 days (presumably for those who may have made booking mistakes), but they do not allow outright cancellation of nonrefundable tickets. AA also no longer allows holding revenue reservations within that final 7 day window.

I've therefore used Expedia for close-in bookings when I've found a good fare that I'm afraid I might lose by waiting to book AND I still need additional time to firm up plans to be sure I can take the flight.

I haven't double-dipped with their rewards program, as mentioned by another poster above, although that may be something worth considering also.

By the way, Expedia still allows you to enter personal details like your AA FF# and US CBP trusted traveler number, so it's possible to earn frequent flyer miles, get elite upgrades, TSA precheck, etc.