The expression of this "new" one comes across with much more self-certainty. Her grin adds a tinge of "I know what this does for you" (in regards to the viewer or the artist). I'm simply comparing the old and the new ones in regards to each other, of course~ Over all she seems more mature.
The old one has its own strengths, of course, but I find the new one to be more honest to the idea of "Powergirl" than the old one, if I were to have to pick one.
I could probably keep talking for another good essay's length, but those are my 2 cents. : P