In the close range, the original Sonar formula is less sharp. By 5.6 they ae equal.
The colors are different on all the original Nikkors single coated. If you put them on a digital camera, and make an image with the Sonar and Gauss same time , same place, you can see the difference, The later multi coated being more accurate. I am working on presets in photoshop so I can get color matches.
The original Sonnar has a very small rear element, the later Gauss a large that nearly fills the lens mount area.
I have one original and two Gauss copies and assure you will be pleased with either.
I prefer the image of the Sonar, but the color of the Gauss, so I fix it in photoshop. My copy is unused mint for all practical purposes and is one of my treasured possessions.