As Dave writes, 200mm gives you more working distance.
However, this is often not the case for internal focusing designs - specially not up close where the 'focus breathing' of the optics loose focal length.
Not all IF designs do,, just see the long debate on this for the 70-200mm f/2.8 AF-S zooms where the lenses behave very different from each other.
So a unit focusing lens is often preferred for macro work when working distance is important.
This is why I love the 105mm f/4 Ais Micro Nikkor. Often the best compromise.
The 300/4.5 ED-IF AI with PN-11, PK-13, PK-12 and full built in focus as **suggested by John Shaw gives an image magnification 0.5x (1:2) with a free working distance of 962mm.
(a Lens cradle is indicated) **John may have only recommended a PK-13 or a PN-11. I don't remember.
The 200/4.0 IF AI with no tubes or close-up lenses offers an image magnification of 0.5x and a free working distance of 495mm.
The AF-D 70-180/4.5-5.6 at 180mm offers an image ratio of 0.5x and a free working distance of only 244mm. (This is good example of what Eric Lund writes concerning IF designs. 244mm at 1:2 is not what one would expect from a conventional or unit focusing 180mm lens.)
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I probably wrote this for a discussion at Photo.Net's Nikon Forum (in a previous life)...
There are two manual focus 105mm Micro-Nikkors: an f/2.8 and an f/4.0. You should consider both. The 105/2.8 AIS Micro makes a good general purpose 105 and macro. As far the change in focal length I estimated it at 92mm for the 105/2.8 Micro but the lenses has CRC and change in focal length seems complex. Notice the free working distance of the 105/4.0 v. 105/2.8 at 1:2 and 1:1. The 105/4.0 AI or AIS Micro-Nikkor is probably the better and certainly the easier lens to use for more serious close-up and macro photography.
Here is a table of free working distance that in includes the 105mm Micros...
Lens, 1:2 followed by 1:1...
55/3.5 Compensating
110mm
55mm
55/3.5 AI
111mm
56mm
55/2.8 AIS
113mm
56mm
60/2.8 AF
122mm
73mm
105/2.8D AF (not my measurement)
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136mm
105/2.8 AIS
244mm
173mm
105/4.0 AI (& AIS)
277mm (The best at 1:2 of this table)
172mm
All measurements are mine except for the AF 105/2.8D Micro-Nikkor. That measurement came from the Nikon brochure Nikon World of Close-up Photography, 1994. Notice that the 105/4.0 AI Micro-Nikkor has the best free working distance at 1:2 by a comfortable margin and is virtually tied for best at 1:1 with the 105/2.8 AIS Micro-Nikkor.
I have no experience with the 85mm f/2.8 PC Micro-Nikkor. If you can afford the 85/2.8 PC you can very likely afford both the 85/2.8 PC and 105/4.0 AI or AIS. The latter can be had for a very reasonable price.
Hope this helps,
Dave Hartman.