I think those are both my favorites as well! I like the vertical one of their backs because I think I really got the effect I was looking for with the lens.
ETA: Ok, so I'm pretty certain the first was the Muse. The focal point of the second seems much to crisp to be the muse, but something about it doesn't look like the nifty-50 either. It has to be one of the two! EXIF does me no good, the focal length is the same for both lenses.