DC based EXP flyer here. Use DCA 99% of the time and rarely go to IAD if I can help it. Granted I'm EXP, but in my experience upgrades aren't that difficult to get. Of course, YMMV and this varies entirely depending on the route and day. I fly DCA-ORD often and several times I've set next to people who had no status and who upgraded for a fee at kiosk check-in.

As for the flight options, I agree with the rest of the posters -- very few cities you can fly nonstop to out of DCA on AA. Although, I like JFK for connections as there are some good times (especially the late night JFK-DCA AE flight for west coast and int'l connections) I've come way too close to misconnecting given that JFK can get pretty bad delays. I find the AE flights from DCA are often impacted much more than AA flights.

Of course, given the perimeter rule no matter what airline you choose your long haul options out of DCA are limited.

Lastly, something else to consider that no one else has mentioned, the AC staff in DCA are terrific. Definitely a plus for AA.