Believer/Unbeliever, Faithful/Infidel, What is best?

A question of properly translating πιστός and ἄπιστος in Byzantine Greek Church literature.
Should they be translated as believer/unbeliever, or faithful/infidel?
The translation of believer is not difficult to accept, though it is a tad ambiguous in today’s English, but unbeliever is too neutral. It does not reflect the intensity ascribed to by the majority of the original writers. Infidel may be better suited. It is a strong word that has near racist implications based on religious grounds, and has especially been propagated by media coverage of radical Islamic actions against those who do not share their beliefs. In reference to some Byzantine Church writings, infidel feels closer to the writer’s intent.

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