Congratulations, giantfox! As you know, both of them are great schools! If you want to more focus on researching AI or applied machine learning, U Mass Amherst would be a great choice! If your research interest is theoretical ML, both are quite good. BTW, U Mass Amherst is not that far from Boston, so you don't need to worry about the location. Some of my friends are PhD students of U Mass Amherst, and they often spend their weekend in Boston. Also, some of them actively interact with guys at MIT or Harvard. Consider your research interests and make a decision for it. Good luck with your decision!