Most students who receive financial aid from the Nic School are partially awarded with a regular scholarship + a one-year assistantship (~10hrs/wk for $3000), which gets converted into a scholarship in your second year. This $3000 scholarship will not be awarded in your second year if you choose to not accept the assistantship, so effectively you are working for $6000. The assistantships could be anything from an RAship to an alumni relations assistant, administrative assistant etc., so you could use it as an opportunity to advance your career. Once you are on campus, the Nic School will provide a list of available assistantships, and you will apply for the positions like a normal job- everyone is guaranteed a position somewhere. You can always find other jobs on campus as well (i.e. library assistant or RA with other profs), without being limited to the assistantship options.
The general impression I got is that Duke is more structured, and the curriculum is designed to help you develop some technical, specialized, essential skills for your topic of interest (at least for energy and GIS). This was what I was hoping to get out of my MEM, so it worked out perfect for me. If your focus is energy, Duke has a hub called the Duke Energy Initiative, which promotes interdisciplinary work between the B school, Nic School, Sanford, Pratt, Medical school, etc. https://energy.duke.edu/ It's not just an on-paper collaboration, but it's fully integrated into the university which I thought was very cool.
Yale on the other hand, gives you a lot of freedom with regards to the courses you can take. All the professors and courses are fantastic, so people who do not have a clear idea of their goal could end up graduating with a broad, general education without developing advanced skills. If your goal is to interact with leading thinkers/policy makers, and to have a better understanding of the big, important ideas, Yale could definitely help you with that. Duke definitely has some great connections as well, but I feel that Yale has an edge in that aspect. Since last year, FES has been trying to address the issue and made it mandatory for students to declare a concentration (if I remember correctly). That being said, Yale only accepts people who are already mature/advanced lol.
Also, I got the sense that Nic School's student body was more entrepreneurial(?), and FES students were more of your-typical-environmentalist type.
In terms of ROI, Duke seems to have an edge over Yale- it may be just because Duke students are younger on average, hence at an earlier stage in their career, so the MEM gives them a greater boost in salary even if graduate from Yale and Duke had comparable post-MEM salaries. I can't recall exactly so you should check the programs' websites. It's all there.
Whether at Duke or Yale, I am constantly drowning in the mountain of opportunities so you can't go wrong with either program. You should also consider things like the geographic location and weather too. I personally prefer New Haven- its right next to the Long Island Sound and a 2-hr train ride away from NYC ($35 round trip), but I feel miserable in the winter months (the lows are averaging -5 Celsius this week). North Carolina is beautiful, but Durham is approximately 3 hours away from ANYTHING (Charlotte, the mountains, the beach, Washington DC; i.e. you need a car), but it is much warmer than New Haven. The Raleigh-Durham-Chapel Hill (the Triangle) area also has some AMAZING Indian and Middle Eastern food. Both cities are beautiful and has a very cool vibe.
I was checking the results for my friend who applied to Duke and Yale for MEM/MESc!
I don't know much about EEP, but if you want to study climate change economics and policy, Duke has Billy Pizer, Brian Murray, and Lori Bennear among others. My friends just attended COP 24 in Poland as a part of a UN Climate Change course https://bassconnections.duke.edu/about/news/bass-connections-class-goes-un-climate-change-conference-poland
In terms of the curriculum, I think EEP is one of the more flexible/versatile concentrations- i.e. energy economics, water resource economics, etc. are cross-listed with other concentrations. Each concentration has slots for "elective courses" for the graduation requirements as well (see "COURSE PLANNING WORKSHEETS" https://nicholas.duke.edu/programs/masters/eep)