from my own personal experience I can tell that most of the time I prefer stackoverflow instead of man pages simply because I need to achieve one task and stackoverflow contains answer of how to do it, man pages can teach me how to do all sorts of a tasks, then I have to choose the right one from those that I have learned.

On top of that, to be able to use man page, I need to know command in the first place, while google will digest my broke english question and point me to the right stackoverflow answer most of the time.