Should I attend Boston University, Boston College or Umass Amherst?

I major in Chemistry (Pre-med track). I plan to apply medical school after 4 years of undergraduate. Which school will give me more advances if I want to apply Ivies for medical schools? Both BU and Umass Amherst are large schools whereas BC has smaller class size. Will it benefit me if I attend a smaller school? (Since I am likely to get internship and research opportunities?)