My view was exactly the opposite. When I book on line I can see the appointment is registered and correct, over the phone I don't know what the receptionist has entered. But the main reason I prefer on-line is because of the silly dialogue with the receptionist which goes something like... "I would like an appointment with Dr X first thing in the morning" "How about Thursday at 9?" " I can't do this Thursday", "How about the following Tuesday at 3pm" "No, it needs to be in the morning" and so on. On-line I just look at all the slots available and choose the best one.