XTR used stainless steel grade 25,
XT probably the same but not sure.
Lower down probably chromed steel not sure of grade.
Stainless has the advantage of not rusting or getting surface damage, you tend to pull them out of old bikes and they are fine and being fine the cups are in better condition.
The chrome steel ones tend to get chunky surface damage (like plate tectonics) this over time has often damaged the bearing surface on the races.
Of course not always either easy and nothing regular clean, dry, regrease would not have prevented.
Either can be used in either of course, though grade 25+ stainless are not the easiest to get hold of. Grade 10 chrome steel are cheaper.
I wouldn't bother with grade 100 or unknown. Mainly as you don't have to, though they would be perfectly fine in a deore hub.