As a Long time poster who only posts about what I know, I would contradict MiamiDAP for the 10th time to say, for a future scientist heading for PhD, UG selection makes a big difference. At Caltech and MIT, it is easy to arrange research programs. This is true for summer and year long programs. Even after graduation, my son wanted to explore research in a different department. They created a position for him, funded by a world re known professor. My son was not even working in his lab.
I am sure there are other colleges that make it easy to do funded research, but I can only mention the two places that I have first hand experience with. Both of these schools have classes taught by profs, with TAs doing sections. They help with assignments, review material, etc. these TAs take their roles seriously.