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HI, It doesn't redirect the user, no. It tells Google 'which URL' you prefer to be indexed. Now, again I don't believe that this is the best option, as you want BOTH cities to rank.  Does it affect the rankings? Yes, because you are saying Page A is more valuable than the duplicated Page B- leaving Page B out in the wild as the less important page for ranking. So, again having two versions of the domains ( based on the cities) isn't beneficial, these should both be under one domain ( wp installation) and adding a "locations" page, to reduce the self competition.