The US Department of Education recently examined the effectiveness of online, blended, and face to face instruction. The results indicated that online learning was more effective than face to face instruction.  However, this seems to be due primarily to instructional strategies and time on task than the delivery mode

Key findings of the report were as follows:
 
1.  Students who took all or part of their class online performed better, on average, than those taking the same course through traditional face-to-face instruction.

2.  Instruction combining online and face-to-face elements had a larger advantage relative to purely face-to-face instruction than did purely online instruction.

3.  Studies in which learners in the online condition spent more time on task than students in the face-to-face condition found a greater benefit for online learning.

4.  Most of the variations in the way in which different studies implemented online learning did not affect student learning outcomes significantly.

5.  The effectiveness of online learning approaches appears quite broad across different content and learner types.

6.  Effect sizes were larger for studies in which the online and face-to-face conditions varied in terms of curriculum materials and aspects of instructional approach in addition to the medium of instruction.

7.  Blended and purely online learning conditions implemented within a single study generally result in similar student learning outcomes.

8.  Elements such as video or online quizzes do not appear to influence the amount that students learn in online classes.

9.  Online learning can be enhanced by giving learners control of their interactions with media and prompting learner reflection.

10.  Providing guidance for learning for groups of students appears less successful than does using such mechanisms with individual learners (Murphy, Toyama, Murphy, Bakia, & Jones, 2009, pp. xiv-xvi)

Reference
Means, B, Toyama, Y, Murphy, R, Bakia, M, & Jones, K. (2010).  Evaluation of evidence-based practices in online learning: a meta-analysis and review of online learning studies.  US Department of Education, Office of Planning, Evaluation, and Policy Development, Policy and Program Studies Service:  Washington, DC.  Retrieved from http://www2.ed.gov/rschstat/eval/tech/evidence-based-practices/finalreport.pdf