Recently US Department of Education has come up with a survey in comparison with online and traditional learning. Following is the report Online Learning Edges Classrooms. Students in online courses learn more than those in traditional college classrooms, according to researchers.
http://www.informationweek.com/news/global-cio/training/showArticle.jhtml?articleID=219400918
In case you are interested to know more about the research, you can find it here:
http://www.ed.gov/rschstat/eval/tech/evidence-based-practices/finalreport.pdf