For macro specifically? Or also for portraiture/general shooting? Which Nikon 105? the 105mm 2.8 D, there won't be much difference. But if you mean the 105 2.8 G VR, that will be a lot faster to focus than the tamron, and probably sharper in general
For actual macro work, any of these will be great. You should be manually focusing so AF speed wouldn't matter
Yes, I would say primarily MAcro work..
The Nikon's AF is very fast for a macro which makes it a good all-rounder as well as for macro. Nikon's teleconverters also work with it.
I always understood that AF did not work with Nikon teleconverters + 105mm f2.8 VR ... so only in manual mode
http://cdn-5.nikon-cdn.com/Assets/C...eleconverter-Compatibility/EN_Comp_chart.html
That is what Nikon say, but I found that AF does work with the Nikon 105 f2.8 VR and TC-14E III when I tried it (on a body that supports centre point AF to F8). It also works with the TC-20E III up to a point - the main issue being when you get close to MWD the reported aperture is > F8 and AF doesn't work