Do you know what kind of originals you are likely to be getting? I would say if it is mostly conventional photographs from the twentieth century or the very end of the nineteenth then a scanner will be more useful. If you envision having to deal with tintypes or badly silvered photographs (or, it has to be said, those annoying textured papers from the 1970s) then a good camera/copystand/lighting setup would be better.
As Mike says, the best bet is to have both

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