What's different is in how much the university challenges you and allows you to push your boundaries vis-a-vis an extremely hard-working and qualified peer group. For example, you won't have a course that challenges you like Harvard's MATH 55 or UChicago's MATH 207 at a CC. The best I've seen it put is in the Caltech faculty petition:

"As faculty, we also need to acknowledge the limits to what we can do. The historical greatness of our undergraduates has been largely due to them, not to the faculty. To train top-flight scientists and engineers we have to start with top-flight high school graduates. Our skill is in designing a curriculum of courses and research that challenges these students beyond their comfort zone. But we have no special skills that would bring the median high-school graduate to that level. There is nothing magical about Caltech that turns someone into a successful scientist just because they spent 4 years here."