Split Testing Ads

hi
When I’m split testing Ads in Adwords / Yahoo, I generally run 2 at the same time, and then I’ll make changes to the losing ad that make it closer to the ‘winning’ ad in terms of CTR.
My question is…
a) Should I Edit the losing ad (to maintaining its history and quality score etc.)
b) Should I create a new third ad, and then delete the losing ad.
i know that both of these methods acheive the same thing, but I wondered what people generally do (the main thing I want to maintain is my quality scores)
Cheers all

Original post by yeahdisk