My advice is to take the full ride + assistantship from GW. I really think that people underemphasize the importance of coming out of grad school with as little debt as possible. GPPI and Heinz are both great programs, but I don't think that they will give you an extremely significant leg up in terms of jobs/career after school over what you will get from GW. There is a BIG difference between 35K in debt and 70K-90K in debt. If you really want to do research, as it sounds like you do, then having an assistantship should be viewed as a huge bonus. If I were in your shoes, there is very little chance I would turn down the GW offer.