One step which might help you decide is to look up the individual faculty members on the economics department webpages of Pomona, Amherst, and UChicago. Which school’s economics faculty has the most publications on significant and interesting (to you) topics appearing in the highest quality journals? Which would be the most interesting and from which you feel you could learn the most given their research output? Which will carry the most weight with graduate school admissions committees when you are a senior and asking them to write recommendation letters? If you are serious about a career in economics it is the personal and professional qualities of the economics faculty that matters. This is the group you will interact with and who will have a major impact on your college education and who may help inform your future career decisions.