If you're interested, go back and look at those two snippets again, and pay attention to the tense. Notice how the first snippet uses passive tense? The environment was changing. Nothing specifically is acting, except maybe the clouds. While in the second snippet, each part of Aaron's face is acting almost of its own accord.
The point is that those are examples of two flavours of action: one passive, one more active. Do you feel how they are different? Do you have a preference?