I suspect NUMBER1BEARSFAN request for something out of IAD for doing a day trip was asked by him because his airline SWA flies to that airport closest to Washington DC, and his airline probably does not fly into the other BWI and DCA airports. That's kind of like me wanting to go to NYC but having to deal with La Guardia or Newark since we don't fly to JFK recently. You can get to Manhattan easiest from La Guardia, then Newark, than JFK. JFK takes a long subway ride to Manhattan, I'd say, at least 45-1Hour depending on the flow.

If Washington DC is what you want, than DCA is the ticket. DULLES I'm sure though a very nice airport, services Virginia area and points west of the Capitol I suspect, and BWI, services mostly BALTIMORE, but you could use all three to get to Washington DC especially if you rent a mobile. But if you want to get to DC, and take advantage of the transportation there cheap, I believe DCA is the way. The other two airports youre going to have to rent a car or take something like a bus or amtrac. DCA is smack on the Potomac. Can drive a golf ball to the White House from there. But not everybody flies to DCA. My airline flies to BWI and DCA from Houston where I live, but you have to go via NEWARK to get to IAD. Maybe your airline goes only to DULLES or only to BWI or DCA. for instance. I had a friend in Baltimore I went to school with and I made a visit. He suggested I fly into BWI, but DCA was open when the flights to BWI were overbooked. He picked me up in DCA but it was really not a big deal. Just a little more of a drive. I never flew into IAD, never seen it. DCA is a neat place to land. You fly over the Potomac and you can see some beautiful landmarks from the sky.