DCA is your best choice without any other consideration. Make sure you calculate the added time and expense of arriving in DC from the other airports if you opt for either BWI or IAD.
------------------
Addicted to airline miles? Check out:
Mileage Workshop --- "You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer." - Frank Zappa (1940-93)