Another intangible that doesn't get talked about much is the baggage delivery speeds at IAD versus DCA.

I've had plenty of times where I get off the plane in the central pier and walk quickly (no more than five minutes from plane to carousel) and my baggage, and ALL of the other bags are on the belt, with the belt stopped already.

Compare that to the long journey (I take my time, on purpose) from the far off gates at IAD, down on the train, the long walk back up to humanity to find that the bags still have at least 10/15 minutes before they are coming off. Add in the people fighting for spaces around the carousel - and I'll again take DCA any time, even BWI is better in this regard than IAD!

-jeremy