David,
Your findings are interesting and also pretty close to what I would have expected. Knowing the kind of work you do and the thoroughness with which you have been developing your setup, I could guess that the particular sample of the Optolyth 100 you have been using must be a pretty well-corrected low-aberration sample. Given such a sample, when looking at pure resolution the 100 mm aperture of the Optolyth should equal or even slightly surpass the performance of the ATX 95 at equal (high) magnifications, and as you well know, any well-corrected scope will continue to show added resolution beyond 1x/mm of aperture.
The Optolyth 100 is very rare here in Finland, and I have only ever viewed with two or three, and that was a long time ago. None of these were very good, but as I said, if yours would not be very good, you would not have been using it for long.
The second observation also doesn't surprise me. The ATX really is very bright, and because of the minimal light loss, has excellent contrast. The Optolyth coatings have not kept up with the development of other top brands, and there can potentially be a 15-20% difference in overall transmission between the two. That will be readily apparent.
Were you able to do any kind of a star/glitter point test with the ATX to determine its aberrations, or was is resolution chart only?
Kimmo