Resampling is different than re-sizing. The latter truncates data and the former averages data in a way that random noise is attenuated but not data that is consistent with actual information. Data that is consistent between pixels in an area reinforces the data and random noise will be, well, random so averaging will reduce its calculated value when combining the data from adjacent pixels to get a new value. The D7000 files can produce great 8mpx equivalent files. Resampling to the equivalent to 12mpx on the D800 really makes a difference. On the web, where anything more then 105 pixels/inch is a waste since most monitors would no be able to display more, cropping and downsizing can just about cancel their opposing traits....cropping lowers res and downsizing averages noise.
There are several ways of reducing the data and some are better than others for retaining detail and canceling noise. If you are using Nikon software or Photoshop, select Bi-Cubic when re-sampling.
All this pre-supposes equal viewing distance and display size, if someone is intent on pixel peeping they are going to find any sort of pixelation, softness or noise that they are searching for. I have to laugh watching pixel peepers who are so used to seeing images way out of normal human scale, visit an art gallery. You can always tell if they are the sort who would pixel peep, they look at a painting from 2 inches away as if that is going to give some hidden meaning or reveal the artist's intention. Any art, has a scale that it meaning dwells in, and far removed or too close and it means nothing. That is the same with photos, but more so since it is so easy to blow it up so beyond recognition as to render it meaningless. Stan St Petersburg Russia