I have used both methods, and what I do generally depends on the situation and how much time I have. Often scrapping can be a little more time consuming than placing paint tape along the edges. So again it depends on the job and there are even times that I do not use either method as there is no need. Touch ups are very easy and sometimes do not require these.

However for first time painters I would recommend the tape method at it would probably be the easiest for a beginner.