Hi! I went to Columbia for undergrad and am now a grad student at Duke, so maybe I can provide some perspective. I may be biased because I just moved from New York to Durham and grew up in the tri-state area, but I thought Columbia was a better match for me than Duke is so far in terms of culture. In terms of the quality of the environmental science programs, I feel like only you can assess if it lives up to your standards, so I'd encourage you to do more research for both schools.
I don't know much about the environmental science program at CU, but I do know some people who majored/minored in it and they had great opportunities to work in the field, whether it was at Lamont or in Antarctica! I took an enviro class there and really enjoyed it. Sustainable development is becoming big in NYC too, so if you're more interested in the industrial side of it I'd imagine there'd be plenty of internships around. I don't know anything about Duke's program except for that they have a whole school for it called the Nicholas School, which seems like a big plus. I'm in the natural sciences and at one of our events, I met many people who are studying ecology, marine science and conservation, etc. so that may be something to consider.
If you don't care about Greek life or athletics, Duke may not be the best place for you socially. At CU, you're not limited to what goes on on campus because you have the whole city at your feet, and it's even easy to take weekend trips to neighboring cities by trains and buses. Also, no one really cares about athletics there partially because the teams are all pretty bad, and also because again, the city is not built around Columbia whereas Duke appears to be the focus of Durham. In my opinion, it's much easier and entertaining to travel around NYC, and there's always tons of new places to check out. When I'd get bored on campus or need a break from studying, I'd get on the closest subway and get off at a random stop and just wander around. Manhattan is HUGE and very easy to get around once you figure out the subways, plus there are four other boroughs to explore! The downside is that it's quite expensive to live there - I can't believe how much cheaper it is in Durham (i.e. my rent with one roommate is $417 without utilities, my friend's rent with 2 roommates in a bad neighborhood in NYC is $1200. A beer at a bar in NYC is $8, here it's $4, etc.).
I will say that students at Columbia tend to be extremely progressive and aren't shy about it - many are into "safe spaces" and frequent small gatherings/protests/marches. Of course not everyone is like that, but it's something to consider. Duke's campus is much prettier if you're into that and the amenities seem better, plus the locals are all very friendly. New Yorkers love to talk too, we're just always in a rush.
TL;DR: do more research on your potential majors at both schools if that's most important to you. Check out major requirements at both, classes offered, potential advisors, study abroad and internship opportunities, etc. because that seems like personal preference, but the Nicholas School seems like it would be good for you. Culture-wise, Columbia might be more up your alley if you're not into athletics or Greek life. As for location I'd rather live in NYC than in Durham any day to be honest but I'm from there so I'm biased. If you can, try to visit both campuses when classes are in session and sit in on a lecture. That may give you a better feel for both. Good luck and feel free to PM me if you have any questions about Columbia/NYC/Duke/Durham!