It depends on what's important to you. Both Winchester and Mt. Sterling are nice small towns with low crime rates and a nice atmosphere, so you've narrowed your choices well. One big advantage Winchester has over Mt. Sterling, however, is its proximity to major shopping and entertainment outlets in Lexington. One of the largest shopping areas in Lexington is situated just off I-64 on the Northeast side of Lexington, so it's literally 15 mins. from Winchester. In Mt. Sterling, you'd have to travel about 40 minutes to get to any major shopping/entertainment venues.
Also, you may find it easier to locate a home in Winchester because most homes for sale in that area are listed in the Lexington Area MLS, whereas many homes for sale in Mt. Sterling aren't listed in any central database (many agents in Mt. Sterling aren't members of the area MLS) so it's harder for you to get a true idea of everything that's on the market in Mt. Sterling, especially from far away.
Obviously, you can tell that as an agent, I favor Winchester, but having said that, both communities are nice smaller towns to live in and I don't think you could go wrong with either one.
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