I fly out of all 3. the advantage of BWI is the less expensive off airport parking. other than that, it is lousy, even as an airport.

DCA has good short term parking. the major airline is US, which is about as lousy as lousy can get. i forgot, dca runs out of parking. the ticket counter for US is way undersized. the line can at times take an hour or two if you are planning to/must do line.

IAD has bad security at times.

they do not give FF points for airports, so go whereever you find your best service. They are about even on delays. Customs in PM is better at BWI(could not be worse than IAD)