Upload & Sell: On
First, coming from someone whose visual acuity is sometimes in question and with my having been told cataract surgery is 5 or 6 years down the road, the first image appears marginally sharper to me. I am basing this on the area of the blossoms on the leftmost figure.
Frankly, I don't see a whole lot to be concerned about. Having been able to resist the calling of a D700 and D800 over the years, and having ultimately settled for another form of camera, I will note that everything I've read about the D800 is that it is a superb machine (often mentioned as the standard for IQ comparison), but it is unforgiving. That is, proper technique is an absolute requirement to achieve optimal results. Assuming no variance in technique, you could perceive a difference in performance in the lens across two platforms.
Or, as Kent points out, underlying differences in the renditions produced by each unit are at work. Truth is, if any of the above, or other variables (MP count etc.) are at play, we'll never know.
Relax and enjoy the new gear!
<later> In addition - for a fair comparison an even baseline is necessary; two D800's - one a known performer and your acquisition.