Timing becomes critical to the effectiveness of drag and the overlapping action. As action starts, we have more drawings near the starting pose, one or two in the middle, and more drawings near the next pose. Fewer drawings make the action faster and more drawings make the action slower. This will give more snap to the scene. This is especially true of the human figure and the action of animals.
Arcs give animation a more natural action and better flow.
Think of natural movements in the terms of a pendulum swinging. All arm movement, head turns and even eye movements are executed on an arcs. The walk is forceful, aggressive, and forward leaning. The leg action is just short of a stomping walk. The secondary action is a few strong gestures of the arms working with the walk.