The only way you will satisfy your curiousity is if you try both, same subject, same very careful focusing, with and without a lenshood, with movements and without. This way you'll be able to tell with confidence, otherwise you'll always wonder what your images looked like through the other lens. Put these test negatives through your usual workflow and analize the results.
Don't enlarge the test negatives more than you plan with your prints, don't use more movements than you usually do. If I understand it correctly, you are not trying to learn which one is ultimately the better, but which one is best for your own needs.
The 32x40" enlargements, while not overly large from 4x5, are at the point where careful technique matters a lot as you already know.
You didn't tell us what your favourite subjects are, at what distance you like to shoot them, what f/stops you prefer, what film you use, how you develop it.
If I'm not mistaken, these data come from a test that was done at 1:20 by Christopher M. Perez and Kerry L. Thalmann. While resolution tests for lp/mm pretty close up is the best most of us can do, it really tells only part of the story even if done very carefully. An aperture that gives the highest resolution (high frequency contrast) might not give the best overall acutance or "impact" (low frequency contrast).
The Fujinon is a Tessar-type lens, that was top of the line a hundred years ago and still highly respectable today. Many believe the 6.3 series is the best of the type. The newest types of the classic 4 elements in 3 groups design stand up extremely well against the more complicated ones, both 35 mm and LF. I personally love them, but they do have their own limitations. So do we, photographers.
Once in a while I test my cameras/lenses at infinity with real subjects and at a distance of 3,5 meters with resolution charts at home. Numerically we can tell quite a bit from the photographed charts (both sagittal and tangential resolutions for example, even if at least my eyes are always a bit overly optimistic) and it's easy to see how resolution changes with less than superbly corrected lenses by stopping down. In the field with the with blowing or without, well, this matters much less.
Although I have no direct experience with the two lenses you mentioned, only with similar ones, I'd say if the slightly greater coverage is of no importance to you, then you are very well equipped with your Fujinon. The quoted test suggests it has more even performance at 1:20 than the plasmat Sironar-N.
If it's greater clarity what you're after, I'd suggest Delta 100/TMX/Acros, with an acutance developer and not stopping down further than f/22. I'd personally rather have a sharp foreground with a slightly out of focus background (and not the other way around) than an overall slightly soft image owing to stopping down too far. And a perfectly aligned enlarger (even though I know no such thing exists, not even in PKM's darkroom
). Maybe you already do this.
I'm not sure if this was of any help. If you can, buy the Sironar-N, spend a day shooting and comparing the results, give it some thinking and sell the one you like less. Try not to keep both.
