I can't be bothered trying to get a rocked chain working good again, that's for sure! More time involved than its worth and they still wont cut great.I can only say "seemed to cut as fast", no empirical data to back it up. Me personally I like a new chain... but some of those guys could make an old chain cut like nobody's business.
I was also the guy at the tree service that made the new loops of chain. There were guys that would have me make new loops at least once a week, they didn't want to be bothered with fixing chains that got ran into rocks, nails or hidden concrete in old trees.