My personal opinion…I would not allow a kid to apply ED to a place they have never visited. Any chance you live close enough to drive to Middlebury…this week? If so, I would suggest you take your student there. Let them see for themselves.
Is proximity to a city important to your son? If so, Middlebury really isn’t near…anything. BC is right near Boston.
I think location might be the difference.
Also, BC is a Jesuit college…and Middlebury isn’t. Does that matter to your son? I will say, the Jesuits really have higher education well crafted.
Both are excellent colleges but are very very different personalities.