To answer Steve's question, I'm sure that hand filing would win out over grinding for longevity.
But there's plenty of other factors. One is how much damage do you need to remove? If the chain is really buggered up, a grinder is probably the better option than filing a chain way back to make it usable. Which brings up the question of how much time will someone spend to restore a rocked out chain? If I bang it up pretty good, I just toss it. Especially if the chain catches something and all of the damage is on one side of cutters. Not worth it to me to spend a lot of time to save a chain; I just grab another one.
I'm good at filing, so I've never considered a grinder for personal use. And I have a lot of saws and like to be able sharpen them without having to remove the chains. I always touch them up before I put them away so they are ready for the next time. Even if they really don't need it, which I know isn't a "mileage minded" way of thinking. For you guys who have a lot a chains for a few saws, then I can see how running them all through the grinder in one clip would be better than hand filing them all at once.