According to a meta-analysis by the US Department of Education, face-to-face courses are less effective than online and blended learning. They caution against viewing this as simply a matter of the medium though. It's the changes in what online and blended learning allow (like opportunities for collaboration) that are likely making the difference.

Direct link to PDF: http://www2.ed.gov/rschstat/eval/tech/evidence-based-practices/finalreport.pdf