That's it as I see it - it's pretty much a time versus money issue. Some people unconditionally swear off the two outlying airports (BWI, Dulles), but all will work so long as you know and accept your transport options.

I find the bus + rather long metro ride (Green line) pretty hard to hack both ways, but if you can do the MARC (or Amtrak) at least one way, it's not too bad. Some have had luck with a one-way car rental having no drop fee between airports, but that's probably not practical here.