Be it a storyboard, an animatic, a photo- or video-layout, I always like to use one or more of those means in oder to determine what the finished film will look like.
On the one hand’s side you can get a good idea if and how the story can be told in the given time (20 sec. can be awfully short!)
On the other side, you can reduce the number of shots to a minimum, which saves production time and thus a lot of money.
For example, the N24 spot was prepared using a video layout and the Blind Dinner Production was planned with a detailed storyboard. In neither production more shots where filmed than those used in the finished product.