I don't know about BU, but GW is really expensive to go to. Not sure about their tuition, but living costs. It's about $1000 (or even more) to have a studio (with no kitchen) on GW campus. But then, plenty of people there don't live on the campus, and they don't live alone. There are a ton of job and internship and research opportunities in Washington, government, public sector etc. not so sure about Boston.
But, again, if you want work in Washington after graduating, then GW is well-recognized in Washington legal market (it's #2 after Georgetown..). You have to think about whether or not it's Boston or Washington you would like to work in.