This debate has been characterized on the Nikon consumer dSLR forum as a “holy war,” and it certainly seems that way to me. The debate is currently maintained by a few people who insist that NX2 is vastly better than ACR for D7000 files. They tend to site sharpness as the main issue, and I’ve had that explained by one of the more credible people as a tendency for ACR to put jagged edges on diagonal lines.
There was another issue but it is so minor as to be irrelevant. Some also cite color as a big difference, but of course ACR is infinitely variable and tunable and so is NX2. NX2 happens to default to camera settings, perfectly matching jpegs from the camera, and beginners especially find that appealing. Enough so that the more aggressive among them think that this feature is a decent substitute for an intelligent argument :-)
So anyway, I thought I would run a really quick test using the D7000 and a Sigma 105mm 2.8 Macro lens with Canon 500D achromat (i.e. high quality close up filter.) This combination shot a window screen that I have against a wall while I shoot moon and planets from my window sometimes.
The flash creates perfect brightness and sharpness and since I turned the camera to about 50 degrees, I also have lots of diagonals. Seems like a reasonable test to me.
ACR converted it with ease. Its sharpening controls are unbelievably effective. A high degree of control and a very fine grain to the adjustments make for amazing detail-pulling ability. I find capture sharpening in ACR to be extremely effective.
NX2, on the other hand, feels like a blunt instrument by comparison. Perhaps there are better ways of sharpening, but in examining the entire interface I found only the same camera controls for that purpose. So I set to the neutral picture control, the same one I use in ACR, then I set the sharpening to 6 out of 10, or just a little extra sharpness. I set contrast to 6 out of 10 as well. And that was that.
The result is that the ACR conversion is vastly sharper. And despite its dullness, the NX2 image has visible halos on the edges, no doubt the product of a very high radius on its sharpening. I sure hope that there is a more advanced sharpening control on this beast because this result just plain sucks.
If you want to tie that back to the real world, imagine how hair would look with each conversion. Closely examine the cobwebs to get a hint.
Caveat: I am an expert with ACR and a rank amateur with NX2, so take this with a grain of salt. But the interface is slow and blunt on NX2 and the work flow sucks. So even if it was better than ACR at sharpening, I would still dislike it.