Looking at the different scenes, I think the strongest composition is the one with front focus. The eye is immediately drawn to the focussed front pencil, which is reinforced by the strong red colour. This draws you into the scene.
The middle focus scene is not helped by the yellow and green colours of the pencils in focus, but it is the next most interesting photo. The weakest photo for me is the one with the focal point at the back of the scene. The eye has to travel over a lot of unfocussed material before finding something interesting and this makes it a weak composition in my view.
In general, this exercise shows the importance of the choice of focal point. It can make what initially seems a mediocre scene in to a very strong photograph and vice versa.