It is always best to avoid remanufactured alternators and always buy brand new. The only remanufactured alternator I would buy is the Duralast because it still comes with a lifetime warranty like their new alternators do, which keep in mind by the time you pay shipping, core, etc it will be about the same price as a Duralast reman.
This is also the same for A/C compressors, always buy new.