So you need something to scribe the fiber in order to cleave it at the tip of the connector prior to polish - or for more general cleaving, if not using a fancy cleaving machine (Which seem mostly to be carbide scribes, I guess.)
Scribes are offered in Ruby, Sapphire, Carbide and Diamond.
Yet I can't find anything about the supposed advantages of one material over the other. All are far harder than glass, which is most of what's needed. Obviously diamond is hardest and most expensive - but "better" or just "most expensive, makes Ogg think must be bettur?"
The first three are about the same hardness, the first two are basically the same mineral (corundum) with different dopants for coloring. So why the different flavors on the menu? Some sort of "I'd rather push my Ford/Chevy than drive a Chevy/Ford" thing with scribe material, or a tangible difference?