To be sure everyone is on the same page: Deburring either refers to removing a wire edge from the outside of the case mouth with a female cutter, or to removing punch burrs from around the inside perimeter of the flash hole. If you buy cases that lack wire edges or burrs, and you are satisfied with their length or are not reaming the flash holes, there is no value to adding the operations. Examples for me are pretty much all Lapua and Norma cases, which come chamfered and deburred around the case mouth and are formed without flash hole burrs.
Case mouths may have wire edges from the saw, though final polishing by the manufacturer usually eliminates them pretty well, leaving only the trim pattern. Chamfering the inside of the case mouth can help smooth seating. Most often, though, if you are making match loads or loads that are to be crimped, you trim the cases to a uniform length, at which point you will have to chamfer and deburr the case mouth if your trimmer cutter doesn't handle that simultaneously.
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