Not a big difference, no. Well, I don't expect it to be a big difference to somebody who's not working on anatomy.
But yes, the surface anatomy is significantly different between the two - I was referring mostly to the neck, though. If you look at the way the light falls, it's different in the painting and the photo - that's the muscles. And the embossments along the spine are also different. I know the level at which the vertebra prominens (the bulge at the base of the neck) is, and it's distinctly at the wrong level in the painting. Notice also that the neck in the photo is an almost straight line along the dorsal aspect, from hairline to base of neck, while in the painting it's convex. It's a small difference and wouldn't have mattered if =
Ninjatic had adapted the muscles and the bones accordingly, but as it is, it emphasises the wrong placement of the C7 vertebra in relation to the other vertebrae.
And to explain what I mean about the muscles, too (because I ended up going into detail about the bones) - the sternocleidomastoid (SCM) in the photo is straight (as a contracted muscle would be) whereas in the painting it's curved in an impossible way.
I love the SCM, which is probably why it hits me this strongly.