If you attend Amherst, you’ll very likely emerge a better educated person. BC is a terrific school, but it’s very hard to “slip through” at Amherst and not really be changed (and I’d say significantly improved) at a school that is as intimate and academic as the 'Herst. I’m a Williams alum, so this pains me to say, but you should go to Amherst.
As for this:
That ranking almost certainly includes (and, thus, is primarily reflects) post-grad programs.