When I was talking to one of my repair guys about possibly getting an FD macro lens, he suggested to me that I should get one of the long lenses, and avoid the 50. He said, "It is not very good." Is there any basis for this statement, or did he just need something to say?
As far as I know all 50 mm +/- macro lenses work very well at magnifications > 1:10. Performance at infinity is another matter; MP and PP never published tests of a 55/3.5 MicroNikkor because no versions of that lens met their minimum standards at all apertures at infinity. Your repair guy may have had/seen an abused 50/3.5 FD.
Unless my memory has failed completely, the 50/3.5 FD was well-respected when new. But that was then. This is now and the FD lenses for sale are all used. So if you get one run it through acceptance testing before using is seriously.
To keep it simple use the 100 f4/FD lens.
My recollection is that the 55/3.5 Micro Nikkor with less than excellent performance at infinity was the older Micro Nikkor Auto with the mechanically compensating aperture mechanism. While the number of elements remained unchanged in the later 55/3.5s, the spacing changed. This caused performance at infinity to improve. Some people suggest that at 1:10 and higher magnifications the older design was better. I haven't seen this myself. I have a black front Micro Nikkor Auto, ten 55/3.5 Micro Nikkors from the P to the AI and a 55/2.8 AIS. They are all very good. If I don't need the speed or an AI lens I like the PC model best. For Canon FD I have two 50/3.5 FD SSCs and two 50/3.5 New FDs. These were very good when they were made and still are. Whether you need a 50 or a 100 is determined by how much working distance you need between the lens and the subject. One is not better than the other just because of the focal length. I have never used any of the 200/4 Micro Nikkors. From what I have read they employ a floating element design which shortens the focal length as you get closer to the minimum focus distance. You might think you are using a 200 but at the closest focus setting you might be at 170. I have had good results using the 200/4 Canon FD SSC. The 200/4 AI Nikkor also works very well with extension.
I have the 100/4 New FD. It's a decent lens but a little dim to focus through. The Vivitar 100/2.8 macro (22XXX...) goes to 1:1 by itself, is brighter to focus through and is also very sharp. My 90/2.5 Tamron SP is the 52BB model. I like the fact that I can use it with more than one brand of camera with the correct adapters. To reach 1:1 I prefer using an extension tube to using the Tamron 2X.
The two shorter lenses I have that use a floating element design are the 50/3.5 Zuiko and the 55/2.8 AIS Nikkor. Both are sharp at all distances but neither will be at its best fully stopped down. Is it a surprise that a 55/3.5 Micro Nikkor is not so good at f/32? Not really. Some sequences from the original Star Wars movie were shot with a 55/3.5 Micro Nikkor. The film was enlarged on a movie theater screen a lot more than any of us will ever enlarge film for making a print. Even the 55/2.8 Vivitar macro has become something of a cult lens. It goes to 1:1 by itself and is sharp at all distances even without a floating element design. I agree that The Manual Of Close-Up PHotography is an excellent reference and I also recommend it highly. Getting quality results in macro and close-up photography requires an understanding of the basics and mastering of technique, not just quality equipment.