Hello Howard,
I can share a little bit on this. The Nicholson #49 and #50 cabinetmaker rasps cut similar to Auriou grain 11-13 cabinetmaker rasps. The Nicholson is an excellent tool, and in my opinion hard to beat on benefit/cost. The Auriou has a little different feel--it feels sharper to me than a Nicholson. If you want a coarser rasp than a 49 or 50, Auriou makes them.
Now the shapes are different. The Aurious all come to a point, which means you can get into tight places. The other thing is that there are no safe edges on the Aurious--the Auriou cabinetmakers rasps, and the modellers rasps like the grain 14 and 15, come to a line edge on each side, and are toothed everywhere. You can cut laterally with it like a saw. So in a situation where you want a safe edge, the Auriou is risky.
The grain 14 and 15 Aurious are finer than the Nicholsons. But a fine file is finer yet. Like for example, in the Euro grading system, the cuts 0, 2, 4, etc. are all finer than a grain 15 Auriou. So the question may be whether you have a need for something in between your Nicholsons and the files.
Hope this helps.
Wiley