I think winners are more likely to get victor type traits, though this could be that in SP the generals that win famous battles for me are normally the ones that fight the most battles, also, in M2, if a general loses one and survives, he's supposed to get a "hates the -your faction-" trait, though that could just be SS6.1 awersomeness showing itself again.

when its all considered, the "oh yea, good battle memories" is a good enough reason to keep them in