I would guess it's all in the details. Specifically, up close you can see certain facial features that imply anger in the image at the left. Further back, you can't see those details any more, but you can pick up on other shadings in the image at the right that we've been taught to signify anger or stress in a face.
Look at the July 11 and July 25 entries of the Mark Schubin Report found here. There's more to it than just a curiosity, it can be used to determine whether your HD display is being viewed optimally.