I live about 25 minutes to DCA and about 35 to 40 to IAD. In general I pick what gets me where I need to go fastest - I travel majority international it's usually IAD.

IAD really is not my favorite. The long walk from the train back to terminal C. The people movers back to customs. The tired C Terminal. Did I mention the overcrowded Polaris lounge (standing room only) during peak hours? Oh, and whoever came up with that obnoxious PenFed advertisement in the walkway, that truly is rhe cherry in top. Ugh.

DCA is nice and quick. Getting in and out driving is usually not.