I used to think I could get a better edge with a file than a grinder until I figured out how to really use one, now all of my chains are super sharp, and as long as I'm not cleaning up a rocked chain, it takes just a couple taps on the grinder to freshen it up once I have all of my angles established. And I don't grind any of my teeth the same length, I find it wasteful especially if a new chain gets rocked, so I set each raker individually by hand so I don't have to worry about them all being the same length.
I still hand file from time to time, but the grinder is for chains that have stacked up over time.
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