Middlebury is smaller and has really great language programs. Dartmouth is bigger but also not too big. It has an LAC feel with the resources of a research university. Quality of life at both schools are phenomenal. Dartmouth is much better for study abroad - it’s academic system encourages people to leave campus and take internships/study abroad during the school year and its study abroad program is the best in the Ive League. Both are great for outdoorsy people due to the close proximity to hiking trails and ski resorts (Dartmouth owns its own skiway though). Dartmouth also has a more diverse student body and the Greek scene is extremely inclusive. Lastly, Dartmouth’s alumni network is unparalleled. You will have no hassle trying to find a job after graduation.
http://www.forbes.com/sites/schifrin/2015/07/29/top-50-roi-colleges-2015-grateful-grads-index/