Hi Rebelslav,
I'm in the similar situation to you, so I can totally understand your feelings right now. Making a decision between SAIS MA and Fletcher MIB is also a tough one for me.
Since I am still an undergraduate student, I'm not quite sure whether MIB program is suitable for me or not. I checked the current student and alumni profile page, and it seemed everyone had at least 3-year working experience. It feels like almost all students have this advantage over me and I may not feel comfortable to be there although I have several internships experience during my undergraduate stage.