i fly in and out of DCA almost every week...USair is big at National. i really didn't understand when you said that you'd probably use IAD (dulles) and that you are going to live in DC proper. if you live in DC proper, then you can metro to DCA (national) but not to IAD. you have to drive to IAD. so...with all that said, i prefer DCA and USair...

hope this helps...