One survey compared the knowledge of students from a distance learning college from the knowledge of students from a conventional college. The results actually showed about a 20 percent greater mastery of knowledge for the students of the distance learning college.
However, most research sees no significant difference between an education from a distance learning college and a traditional college. In cases where the difference was borderline significant, it was usually the education from a distance learning college that appeared superior.
Keep in mind that the tendency for a distance learning college to, perhaps, be better than a traditional on-campus college education, may be due to the students who usually apply to distance learning colleges. They tend to be more motivated, experienced and mature; thereby bringing classroom “discussions” to a different level. My experiences in classes with older students have been much more enriching for me than classes with less experienced students.