@3emigos, My son looked at all of the schools on your son’s list except Middlebury, so I can’t help with that comparison. I don’t remember why Middlebury wasn’t on the list. (I think it was because he was looking for strength in visual arts.) If your son likes Williams and Hamilton, then I would think a visit to Middlebury would be worthwhile.
He applied to Williams ED, was accepted and had a great four years. We’ll never know which of the others he might have been accepted to but his top choices would have been Williams, Hamilton, Wesleyan (and Kenyon). Culturally, Swarthmore and Haverford weren’t his cup of tea. And Tufts? I think it was crossed off the list because it was less LAC-like than the others. He lives in Boston now and would agree it’s a great college town. Williams and Wesleyan are actually quite different culturally --Wes is more activist, Williams more middle road – but they both appealed. Sometimes, there’s no good reason; it just clicks.
For my son, Williams’ insular mountain setting was a big plus. He wasn’t involved in any organized team sport, but took full advantage of the outdoorsy activities. I wouldn’t call Williams kids jocky, but they are certainly active. My son liked Hamilton for the same reason, though Hamilton is smaller and even more isolated. [To clarify: Williams has an enrollment of around 2100 students, so smaller than Middlebury and Wesleyan, and larger than the others.]
Other points of differentiation that might make a difference are Winter Study, the residence hall entry system, the Tutorial Program and a pervasive emphasis on music and visual arts. For my son, these were major positives, along with the many outdoorsy activities offered by the Williams Outing Club.
Williams has a superb environmental program, with majors in Environmental Science and Environmental Policy and a concentration in Environmental Studies. It also offers majors in Political Science and Political Economy with a synergistic connection to the graduate program at the Center for Development Economics. Double majoring is fairly common.