The thing about the Spencer is: It's an elegant example of efficient engineering; it has a refined and balanced visual appearance in an artistic sense; and it's a significantly interesting historical artifact for its use of shelled ammo and being a repeater -- "state of the art" for the period we are interested in.
In one sense, it seems to me this arm is not so completely outclassed as a combat weapon that it wouldn't yet today be effective in some limited patrol scenarios (I don't mean the antique, but the design produced as new), in that the caliber is a body stopper. But I'm not a veteran, just a pretender, so if anybody has a more experienced outlook on that...