Nikkor 35 f/2 vs. 18-200 comparison images
I am wondering about that myself, it's a new lens and I have just
had a chance in the past couple days to do this level of
examination. It may go back for a replacement.
Maybe a high contrast subject in natural light is more suited. I think the reflections of the flash reduce the contrast. I also think you should post either the full resolution files, or crops from the center and corners. With the current size (and subject and lighting), it is not easy to see the difference.
An alternative: take a few pluche teddybears and shoot them with enough flash power. That always gives me nice high contrast images with a lot of fine detail (the hairs). Additionally, you can use the flash in remote mode to increase the angle between the flash and the camera.