Not sure if you have already visited both schools or not, but that is something that helped me make my decision. Meeting with professors and looking more into what research is being done, what the students are doing and have done, etc. is what helped me realize that I would most likely regret choosing the full-ride over the school that I reeeeally wanted to go to, despite the monetary circumstances.
I think it really depends on how committed you are to a certain area of study and work. If you think HKS will get you where you want to go and Ford School won't, and the loans aren't too insane, then I say go with HKS. However, if you are ambivalent or see a way forward through the Ford option, then I say go with that because you'll be more free to make decisions not based on money.