Hmm. Well, in terms of galactic perception. I'm gonna say the old republic is again best, as 'good' and 'evil' were clearly defined as republic/jedi and imperial/sith respectively from a neutral civilian point of view. 

Number wise though, i'd say the legacy and clone wars eras would be best for such small numbers. Mostly because both sides had significantly reduced in terms of military numbers during said time. However keep in mind that, the closer to the legacy era you venture, the less likely it is that they'd have former sith or sith-esque individuals in thier ranks. Or would come into contact with sith at all. It'd also be easier to justify them being able to recruit so many individuals into thier ranks unnoticed during the old republic era, due to the war and influx of force sensitives at the time.