Ceramic burrs are more brittle than steel so you could chip the ceramic burr if a very hard rock was hiding in the beans.
Ceramic burr vs steel burr.
Ceramic burrs are harder than steel and last on average about twice as long as steel burrs.
They will remain as sharp as they always were.
In my very very limited personal experience of n 1 my authentic hario skerton 50 s ceramic burr 5 wings got one of its wings completely chipped off after 4 5 month of intensive use.
For a couple of reasons.
I ve never read that ceramic is more durable than steel.
And boy was that thing slow even before it got chipped.
In fact i ve read the opposite.
In answer to your first question i do prefer the kyocera to the traditional box like grinders with steel burrs.
Ceramic burrs are harder than steel and tend to last longer but they are more brittle compared to steel ones.
The main advantage of ceramic burrs however is that they do not blunt.