Hm, the top right one in my opinion looks much too dark... I don't know exactly how to go about it, but I think if you applied the shadows like the one in the bottom right to the one on the left, but even more moderately (if that makes any sense), it'd be a nice balance. That's what I think though, not entirely sure...

First or third, I'd say. I agree with the above comment that the second one is a bit too dark, feels like too much detail is lost in the shadows.
And as much as I love your graphic shading, I actually quite enjoy the first one's simplicity. It would look great colored. :)

In order: First, third, second. This is mostly because I tend to like seeing shadows done with either hatching or in the colour, but the way you do it works very well. 2 is good but it feels more at home win a noire style comic, like Sin City.

Well they all work pretty well, but the one with the darkest shading is not exactly my favorite here, I do like the other two a lot, the shading style seems to just click better, I mean, the first one with the varying line weights looks really good, it is a good base and it is just clean and looks good. The one with a little bit of shading adds some nice depth and shape and looks good even without color. I can't figure out which one I think works better. The top one is good for harsh light but it lacks the same definition.