I got off my backside and, spurred into action by Qmechanic, proposed closure of the earlier question.
I think that is the right decision here. The recent question is not quite as clear - I'm still waiting for the OP to confirm that he is asking about sub-atomic particles rather than macroscopic charged bodies - but it is broader and the answers are considerably more developed. It makes sense to me that further answers should be posted where they are most likely to be found - on the more popular question.
That was quite an easy decision. Generally it isn't easy.
Suppose a new question is posted and gets several upvotes. However, before any answers are posted an exact duplicate is found, with one answer which the OP finds unsatisfactory. Should the new Qn be closed? According to policy, I think it has to be closed. But if it is closed, the OP is unlikely to get an answer, unless somehow the earlier Qn is publicised. This situation seems bad for the site as well as for the OP.