I'm a bit lost myself to be honest. Haven't visited any of them, or the cities for that matter. So unlike several people here, I don't have a pre-established network, so to speak, in either Washington or Boston.
A professor of mine (who wrote me a reference) suggested that I go through the faculty at each school in detail and look at their areas of expertise, research interests, etc and then try and identify the school which I'm most compatible with. I think that's pretty sound advice. Other than that, waiting on scholarship info from GT and SAIS for the moment.
Sorry I couldn't give you much of an informed opinion. Congrats on your acceptances!