I own(ed) most of the Nikkor's micro lens range and know for sure the 105/2.8 is the best. Image quality, sharpness, shooting distance are the best for MOST shooting conditions. Nikon AF-D 200/4 is great too, but in many cases 200mm is too long for hand held shooting, while 105/2.8 is easily handholdable.
Another advantage is it can be used as a portrait lens, and it does produce great results too.
Can't think of any drawbacks... maybe slow AF on AF-D version, but this is fixed with Nikon's latest AF-S VR version.
To sum up, if your looking for the best macro/portrait lens, so for 105/2.8 !
This lens produces great images of really small things. It was my first 1:1 lens and still has some of the best resolution of any pictures I've ever taken. A very sharp lens!