It's not a matter of one form of teaching being somehow "better" than another, we should be investigating how learning can be fostered using a good mix of the various tools and learning situations available today. It's a bit like investigating whether students learn more in a modern well-equipped classroom compared to a more traditional classroom. It all depends on what goes on in there, who teaches, what methods are used, students' attitudes to the course being taught, exam contraints, class dynamics and so on. The room in itself does not magically lead to better learning just as the mere use of computers or mobiles or whatever will not magically lead to better learning.
Computers are no magic ingredient; it depends on what the teacher and the students do with them. That's what we need to be examining in research. Simply face-offs between online and classroom prove very little and simplify the issues.