The original seems to have a lot more angels in the shapes as well as the rendering of the values. Your lines are a bit more curved and smoother if that makes sense. In the original some areas like the right arm have lines forming into points. I like your values a lot in the study. Another difference I notice is your work is more realistic proportion wise compared to the original piece. I should say feels more realistic. It's still stylized, but, I would say keep pushing the shape. Emphasize those angles a bit more. Still an overall good study. The contrast of values are really nice to look at and I personally like the smoother feel to yours a but more.