Academically Williams and Amherst are identical twins (though I would give Williams the edge in math/science.) The major point of differentiation is location – Amherst lively small town, Williamstown insular mountain village. Amherst is part of a 5 college consortium. Williams has Winter Study (January term) and tutorials (2 students/1 professor).
Both have very good to excellent med school placement and advising. Williams says
Here are links to Williams’ health professions counseling programs. I don’t know how it compares to Amherst’s, but I can attest that Williams provides robust guidance.