Junior colleges offer lower tuition rates than universities because of local, state, and federal subsidies that help defray the costs that would normally be passed on to students. This makes junior colleges ideal for lower income students to get an accredited education. Universities charge higher rates, but are often able to deliver a better return for the students in the form of equipment and teachers. This is, of course, a generalization based on the best universities. There's often very little difference between the education you can get at a junior college and an average university.
The educational needs of the community are a major consideration for junior colleges. It's expected that the majority of junior college graduates will remain in the community where they were educated, so the programs offered by junior colleges reflect the needs of its community. Universities tend to have a diverse student population and offer a more varied array of courses to attract students from a much larger geographical area.
Because junior colleges enroll students mostly from their own community, rarely do class sizes exceed 30 students. University undergraduate courses can reach class sizes of 100 students or more, due to the large numbers of freshmen and sophomores from all over the world who enroll every semester.
College life is seen as a right of passage by many high school graduates. It's their first time away from home and gives them a chance to develop into adulthood while remaining in a stable and protected environment. Junior colleges don't offer much in the way of college life since they offer no on-campus housing. Universities are communities within themselves that foster an intellectual environment both in and out of the classroom. For this reason, universities tend to create a more intellectually charged atmosphere than junior colleges.
Universities offer bachelor's, master's and doctorate degrees, while junior colleges offer associate's degrees that will typically transfer to a university when students choose to continue toward a higher level degree. Attending a junior college for two years can help defray the cost of higher education, but there's a certain amount of readjustment that takes place when changing schools and students should be sure that their junior college courses will transfer to their university of choice.