Hey rose1 - I'm making the decision between SAIS and Fletcher, and am ultimately deciding on SAIS. I had a lot of the same impressions you had, which is nice to have reinforced, but here are a few other things I noticed. By the way, I went to Fletcher's admit day too, but could only visit SAIS on a random day.
Fletcher: I had a great time talking to my host. I feel like they must have paired us up for a reason, because she's doing the same things I would want to do. Sure, she was busy studying and working on her thesis (very practical topic), but I didn't get the impression that she was all too busy or freaked out, but maybe that's because she already had a job lined up? I really loved the way they ran the open house, and every communication I've had with this school has told me it's very open and everybody is super willing to help you out, more so than the other schools. I also sat in on a number of classes (didn't go to the career services talk) and felt comfortable with the level of the material being covered.
vs. SAIS: Everybody has been telling me to go here since I want to concentrate in economics. I was offered more money to go to other schools, but after seeing both, talking to plenty of students, attending lectures, and pretty much memorizing the admissions sites, I feel confident that it's worth it for me to invest in going to SAIS. Academically, they delve deeper into the subjects, including the quantitative aspect you mentioned. They're known for this, and students are hired more easily as a result. There's also less "explaining" of your degree and what it means, which you also mentioned. Sure, there are more prerequisites for courses, and that's why there's pre-term, but I think it's fair if you're expecting to really master the topics you're studying. Fletcher classes ultimately seemed to lack that depth. SAIS is relatively much more structured, which, having had a very flexible (almost too much so) undergrad major, is something I can appreciate. I, too, am concerned about the concentration and finding a good fit, but I would encourage you to reach out to admissions to put you in touch with an academic advisor. I did that and now feel so much more confident that I can do what I want there, and that there is more flexibility than I thought. Language-wise, Fletcher doesn't expect students to continue language study, but at SAIS, it seems very well supported and covers more languages. I know I can't pass my language test right now, so it's definitely a factor for me. The way it was described to me, in one semester it's reasonable to take 4 classes at SAIS, and either take a language, do an internship, or take a 5th class. It turns out it'll be the perfect fit for me and I can't wait to start.