To answer the question, I have to say I can't, cos don't know.
The names seem to be interchangeable, but I'd always thought that the Nikkor might be a slightly cheaper version. However, folk with lenses marked thus, do not seem to think they've gone down market.
I got a D50. The 6mp has never been an issue, and the money I saved getting a 'Refurbished' (obviously untouched) meant that I could put the 15-55 lens to one side, and get a good lens (off Craigslist) for the difference. my 18-70 really is a serious piece of kit. Good light-gathering with its 67mm glass at $240 used.
The higher pixel count is tempting, and I've looked at higher end cameras to get the detail. But the fact is that it just isn't worth having a lesser quality camera just to get more pixels. Wanting to print out to very large photos might change all this, but I do put the pics on a 50" hi def, and never have I been troubled by pixelation.