Very nice model.

I think it you setup your lighting to match that of the image, then there won't be as many issues with resemblance. As it is your model seems to have a softer face, less defined (in form/presence). That's because the shadowing of the face merges with that of the neck. If you look at the photo reference, the face is highlighted until it breaks at the jaw line, giving way to shadow. This really defines the structure of the face, and gives it a lot more presence.

Your model might be a 100% accurate, but will not match the reference if the lighting doesn't match, so a lot of the time you (and others) might think the model if off somehow.

Just a thought, anyway, it's a really nice model - nice resemblance.

*EDIT* this latest image is getting very close to the reference's lighting.