An LAC of 1000-2000 students may have very limited science offerings. Some courses may be offered only once every other year, making scheduling difficult. Even so, some of them still have great professors who spend a lot of time doing research with students. When you get to LACs in the 4,000-5,000 range, typically the science departments are larger, courses are offered with greater frequency, and more esoteric 300 and 400 level courses will be offered. Many LACs have top of the line equipment - not nearly as many pieces as an R1 university, but the competition for time on the equipment and for research positions working with professors - not graduate students - is not as fierce. I agree with Happy1 - so much of the difference is really about the experience a student is looking for - some kids are natural LAC fits, some are natural large university fits. Figure that out, then start visiting some schools. Ask about awards science students have won, national conferences they’ve presented at, how many research hours students can get. Have some conversations about graduate school that go beyond the “100% of qualified students get in” and get a feel for how supportive the faculty are. I know many MDs and science PhDs who started at LACs and then attended R1 universities for graduate/medical school.