Do you still need help about this?
I just graduated from SIPA and my only recommendation to you is to pass! You will have never met any other group of people who are so unaware of what's going on in the world. I started as development but finished as HR. The only good classes I got were from the PolSci departments Phd classes. Also you have to fight for absolutely every class. There is a period called shopping, in which you go to a lot of classes, but they don't nearly offer enough, so for almost every class you have to submit a statement for why you should be in the class.
For SAIS, i've only heard good things about them. But they would not compare to LSE. Nothing would compare to LSE. I suggest you take it and don't waste your time on SIPA. It's also very expensive. It was my most expensive mistake!
p~