Hey, first of all, congrats on all these acceptances! I think the question can't be answered without looking at the cost of each program. I honestly think the UChicago CIR program has the best placement into top Ph.D. programs (I have seen a lot of people in the top 10 PhDs who have done this program before, whereas none whom I remember did the Georgetown MAs). The Tufts one is very professional work (diplomacy/think tank etc...) orientated and doesn't place as well into top PhDs. SAIS does well if you want to do a PhD in the IR subfield. But still, how much aid did you get, and how much will each program cost you?
Secondly, may I ask why not any UK masters? I think LSE (Government/Methodology) and Oxford (DPIR/OII) place very well in top US PhD programs. Plus, they are cheaper and the cost of living is cheaper. It would also be easier for you to attend, and possibly get better scholarships due to the Irish-UK relations (I may be wrong on this).