Thanks all for the thoughts. I have only a very limited military up and running, so I have flexability as to the type of dwarf I put it on. That is to say, it could go to either a marksdwarf or a melee dwarf. It seems like maybe I'd want to put it on the marksdwarf, if that's the only question that I need to answer, right?
I agree on the skill thing. I think that if I have a high skill shield user (which would have to be trained up in combat in the future once my military materializes), the artifact would be better as his/her raw block skill, plus the bonus from the artifact quality, would make up for any lesser coverage. Yes, that's anecdotal, without actual science behind it.
Also, yeah, in the end it's not that deep of a question because I'll end up with, say, 10 dwarves, one with an artifact bone buckler, and 9 with candy shields, or 10 with candy shields. Just for fun's sake, I should probably just throw the buckler in there, and leave it at that. Figure that if it is inferior to a candy shield, it's probably not inferior by much. I guess I was just curious as to which one ends up being more effective, which can really only be determined through usage and observation I suppose.
Thanks again though for your thoughts so far
(EDIT: What would happen of I did equip a dwarf with both? I've heard that talked about before, but I've never done it. They'd both be light, so the dwarf wouldn't be a killing machine but...I guess he'd be one hell of a meat shield wouldn't he?)