I was going to hail you and ask if you had any more thoughts about the Norton stones. I am still intrigued by the idea of buying a crystolon stone. They are relatively cheap. It sounds like you have had a good experience
Crystolon stones are vitrified silicon carbide. Silicon carbide is sharper and harder than aluminium oxide.... I believe that makes it well suited to bulk material removal but not so great for polishing (scratchy finish). On the other hand... aluminium oxide apparently breaks down faster exposing fresh cutting edges leading to a more polished finish (lest scratchy pattern).
Perhaps this partially explains the abrasive 'rounding' that
@M1k3 mentioned? Once they are round they cut less efficiently and are harder to fracture?
I wouldn't be surprised if all shapton/naniwa (etc) stones were some binder that included either SiC or Al2O3... they are the most popular abrasives. Maybe SiC at the low end and Al2O3 at the high end?? Mostly speculation there... I guess it is possible they use other abrasives (zirconia, boron,....). But I'd guess most of the magic happens in the binder...