I think it depends entirely on the job in hand. I use Dreamweaver to build and design pages and that comes with a built in ftp client. You can set it so that when you hit the save key it uploads any changes instantly if you are logged on.
On the other hand, if I've written a quick page in html in notepad etc, File Manager can actually be quicker if it is just text, though I rarely do things this way now.
I think it depends entirely on your knowledge of ftp clients and the host you are signed up with, there are some hosts that don't allow the use of ftp clients :nuts: