What am I trying to shoot? Natural subjects for the most part, still and moving. I guess the Nikkor would be better there.
I don't shoot Nikon, I shoot Canon, but as someone who shoots 98% macro (nature shots), the principles I've learned will apply to Nikon.
This probably isn't going to be the answer you want to hear, but I personally have 3 macro lenses (100mm f/2.8L, 180mm 3.5L, and the MPE 65mm 1x-5x), and I use all 3 for different reasons.
Nikon does not have an equivalent 1x-5x lens like the Canon, but with reverse-mounting lenses, or bellows/extension tubes, you can achieve similar results. So, if you really want to get "ultra-close," and go beyond mere 1:1 magnification, these things can be handled by Nikon in a different way.
Assuming you're just speaking of 1:1 "field shots," your choice will ultimately be between the 105mm and the 200mm Nikkor lenses (or you'll ultimately get both, if you're like me). So I will try to describe the differences.
The 180mm is my favorite lens of the lot of them, as I think it takes the best overall "artistic" results. When I have a tripod, and can really take the time to compose my shots, I get the best results with the longer lens every time. This applies to nature shots where, say, I have a butterfly on a flower (or just the flower itself), because it gives me the working distance not to scare-off any live subjects ... and, because of that extra distance, I get
a better, smoother bokeh because I am limiting the
amount of background that needs to be rendered. Therefore, for truly nice "keepers," I think you'll repeatedly and consistently get the best results using a tripod and a 200mm. Hands down.
However, if you're hand-holding, and especially if you're dealing with moving subjects, the 200mm and a tripod will likely create more frustration and "missed shots" than anything else. In this case, the newer 105 with the VR would definitely be the way to go. Again, I have both equivalent lenses with Canon ... and I use both because each carries certain advantages the other does not ... and, if you do a lot of moving subjects, and especially if you're doing videography, the 105 with stabilization and the faster AF will be be the way to go.
Me, I tend not to bother too much with moving targets, I almost never use AF, so I prefer the 180 and leave the 100 at home (or in the bag) more often than not. If I pull out another lens, it is usually for ultra-close shots, and then I will use the MPE-65mm and a diffused Twinlight flash. But you may be after different things ...
That said, if you're only looking to get one lens, and you're working with moving targets at all, then I would start out with the 105 mm because it can still get great shots on a tripod ... and it can be pulled-off when needed & be lighter in the field, while giving you faster AF + image stabilization if you're dealing with a moving subject.
Hope this ramble helps steer you in the right direction for your own interests
Jack
PS: The Tamron is a fine alternative choice, image-quality-wise, but it is kinda flimsy in the build quality department. What I dislike most about the Tamron, however, is the front element extends
out toward the subject, which I try to avoid myself (although I have to put up with it with the MPE 65mm).