If you want to see the difference in sharpness between a D600 and D800/e, use FoCal and do an Aperture Sharpness test on each back-to-back under the same lighting and target conditions using the same lens and focal length. I did that with a D800 and D800e, and sold the D800...and bought another D800e. The difference was dramatic.
By the waay, Reikan Technologies says such a comparison is not yet valid with ver 1.6 of their software. However, I did enough testing that I was sure of the difference.
Visual comparisons even down to the pixel level are hard to do except with fine details and with high contrast. You certainly cannot do it with images displayed through the Internet. I compared RAW files down to the pixel level with black/white FoCal target images, and I could see a significant difference when viewing details that were less than 5 pixels wide (i.e., hair, feather patterns, etc.).