My fave would have to be the top one by far. The face has well proportion and it seems to flow the best out of the three. With that saying, I still like the other ones as well.
I strongly suggest you color the last one in, I think it would greatly benefit from color unlike the others that stand perfectly without. With the simple line work in the last one, its making my eyes go cross eyes with all the circles and all the circular/curve motion going on. But aside from that, you got a good bunch of art here