Ginnifers hair works here because she has lots of choppy layers on top, which add height and actually elongates her face.
Halle Berry's face is oval but her hairstyle shown works for round face shapes because like Ginnifer she has the height in the right places. Have the height on top makes her face appear to be longer.
I love Kirsten, I do. But, in my opinion the hair shape on the left is all wrong for her. Where her bob lays at the jawline, it actually makes it look wider. But notice how the bob on the right elongates her face. Amazing right?