Adlnfinitum- I am also facing the same decision. I will be attending Yale's open house April 4-5, but will not be attending Dukes (but I plan to visit separately). Are you coming to Connecticut in April?
What concentration are you, and what direction do you want to go with your MEM? Are you interested in working in any of Yale's centers?
Honestly, I have found it very difficult to find solid information that compares each school, but it appears they are clearly both strong schools. My specialization at both is energy and environment. At first glance, it appears that Duke offers more energy courses than Yale. I am still working on getting complete information about this. As you may know, Yale allows 50% of coursework to be taken outside of F&ES, which allows for all professional schools and the graduate school (assuming you have the pre-requisites)
I have heard that the Duke MEM is more "science based" and Yale is more "social science/interdisc.". I may disagree with that, considering it is up to the student to seek outside courses from other departments if they wish. I plan to take a lot of course work at SOM, Law School, Geology & Geophysics and chemistry dept. Assuming that's possible.
I'm interested to know what you've heard. I also started a thread in "Decisions, decisions", called Duke Nicholas vs. Yale F&ES. Hopefully we can get some responses going there.