Ceramics make some sense (sort of) in very high performance applications if the bearing surface is designed for them
If the bearing surface is of the right material, you can run oil not grease (since the main reason to use grease is to limit corrosion and with ceramic balls on, say, a stainless surface, there is no corrosion risk to speak of), which reduces the viscous preload on the bearing ... but although the effect is measurable, it's not significant in the context of normal use.
Hybrid ceramics only really work at all in cases where the bearing surface that the balls are running on is already of exceptional quality ... and so the limitation of smoothness transfers from the bearing surface to the balls. Not many makers *really* have surfaces of that quality and the distortions in surfaces caused by practices like interference fitting can easily put paid to the concentricity and alignment of the bearing components anyway..The bearing components are limited in their performance, in their turn, by the accuracy of manufacture of the seats that the bearing surfaces are pressed into or the accuracy of manufacture of the axle and associated hardware that the cones (in this case) are fitted to and with.
