As giffenk says, everyone is different. Online wasn't offered at the shop in '05. I took the two weeknights for 3 weeks then ocean route. Later when DMing OW weekend courses I came to the conclusion that one of those would not have been for me--too much in two days. Some instructors at the shop liked online because students did well on the exam, as boulderjohn said--I imagine also because that left some more time for pool. Some instructors didn't like it when they called students days ahead of the weekend and found some were just getting started online. Personally, I've never seen the online stuff, but would think it would've been great for me. In a situation like that you probably could review a lot when you didn't understand something and skim through some of the obvious stuff. That has a lot to do with how much experience one has in the water to begin with. Just some thoughts.
As a school teacher in the '80s I often thought when VCRs became popular that it would be great if they could ever figure a way to get each parent one so subjects like math, science, etc. (those with material that just needed to be learned, not discussed in a classroom) could be done at home. What a saving on wasted time in school with a class of 30. Guess I was way ahead of my time--online in the 80s.....