^^ @dfbdfb
Sure, all those differences are part of the picture. No LAC has a medical school or operates a DOE national lab. Graduate students get more opportunities than undergrads to claim major research project roles. But surely, undergrads get some benefit from those projects. If nothing else, major research opportunities and facilities tend to draw many top scholars, some of whom actually teach undergraduates (or mentor junior faculty).
The OP is considering UChicago. She says she likes history and politics as well as STEM. She likes discussion-based classes. UChicago has about 2x -3x as many undergrads as some large LACs. Nevertheless it has a higher percentage of “small” classes (78% < 20) than some LACs. Yet it employs about 3x as many history professors as Middlebury does (~48 to 16). Now, about 100 graduate history students must command a lot of faculty attention at UChicago. Still, even if the total history S:F ratio is better at some LACs, you’re likely to get far more coverage of centuries and continents at UChicago than any LAC can possibly offer. Is that wider coverage more important than exclusive focus on undergrads? Personally, since you can’t study too many centuries/continents in any depth, I’d tend to recommend a higher level of student-faculty engagement to a greater variety of courses. But it depends on what you want, your learning style, etc.