How should I compare overall college fit between UIUC and Amherst College?

For the priorities you named, Amherst College is likely the closer overall fit: its small, residential liberal-arts environment is built around close faculty access, broad exploration, and a tight campus community. Amherst’s open curriculum gives you unusual freedom to sample fields without a long list of general-education requirements, while its small classes make discussion and professor relationships central to the academic experience. You can also take courses through the Five College Consortium, which expands options beyond Amherst without giving up the small-college home base.

UIUC offers much greater scale and depth in certain areas, particularly across engineering, computer science, business, sciences, and research. That breadth can be excellent for a student who wants specialized courses, major research facilities, a large alumni network, and many student organizations, but navigating academics and social life requires more initiative. Introductory classes can be large, and the experience varies substantially by college and major.

The daily environment is a meaningful difference. Amherst is a small town campus where classmates are more likely to become familiar faces across classes, dining halls, and residence life; UIUC is a large, energetic college town with far more people, events, and subcommunities. Visit or compare a typical weekday at each school: picture the class sizes, how easily you would seek office hours, whether you prefer knowing a smaller circle well or choosing among many groups, and the financial difference after aid. Those practical details will reveal more about fit than prestige or program lists alone.