Click to enlarge, btw.

If you look really closely at the first two, you will see a little bit of difference int he skin, that is mostly from the displacement mapping, which in my opinion does add some nice realism, but is not overly needed, depending on situation.

I like that in the third image the skin looks a bit softer, but I would really have to play with the lights to get a better effect.  I could argue that the AO isn't needed, mind you, in this type of image.  There is nothing I can see of added value.

Notes of interest:  What's up with the hair?  It actually rendered better in the P4 render.  Well, that is to say, it rendered properly with the P4 engine, and it is a mess in the two firefly renders!

It's a Koz hair and honestly, this might be my first time employing it! LOL.  I just wanted to throw some hair on so she wasn't bald!  Weird.