Use Contrast In Orientation
To Focus Attention
The fourth ballerina is backwards and that gets your attention. She stands out from the crowd.
When all the ballerinas are the same they all have equal visual pull; you tend to see them as a group. There is harmony but less excitement. There even seem to be less movement.
Imagine these silhouettes appliqued on a quilt. Which grouping makes for a more attractive quilt? I choose the first one.