Well, I'm biased, since I did my undergrad near Baltimore and I just love it there, but JHU's recruiting weekend was awesome (I went in Jan) and the people there were cool. Plus... its Hopkins, so its world-renowned (is that the right word? i bombed the GRE verbal) Duke was my other choice, but I haven't heard from them, one of the guys at the CMM weekend said Duke lost his application, and JHU was my top pick anyways. But Duke is great too, ridiculously pretty campus. Good luck with the decision making! Both are top universities, so congrats on the offers.