Here's what stands out to me: 1) the skin looks too reflective-very contrasty as if it's made of metal. So you end up with really dark darks and really light lights everywhere, creating chaos. You wanna save your high contrast areas for the focal point 2) the colored one looks grayed out, creating a very sickly, dead feeling, like a zombie. Flesh has reds and pinks and sometimes greens and blues and purples. It's not just tan over a grayscale underpainting. That gives you zombie flesh. 3) the feet are almost exactly the same in both of these. In animation they call this "twinning." When both the feet look the same, it is boring and unnatural looking. Even if the reference is that way, you'd be better off adjusting it. Edit: I'd also play down the ribs in the second one. Even in the photo they are distracting and "samey" ( the design is too repetitive and doesn't create an appealing shadow pattern that helps describe the form)

They both look really good! I would say the way you used thick dark lines in the first image sould be more focused around certain areas you want to draw attention to. Those heavy lines remind me of how product designers manage to instandly draw the eye to details. Overall i guess my attention is just "jumping" between details instead of "searching" for new ones. I dont know if that explains what i mean... AS of the second painting id have to see your reference to critique anatomy.