I never want to turn a thread into filing vs grinder. I do both and believe anyone who seriously uses saws MUST know how to hand file to a reasonable standard. A file can be easily packed & taken anywhere, a grinder usually spends its life in the one place. I used to finish work and hand file all my chains from the day which would include pole saw chains, top handles, and either 50/60cc saw and either 80/90cc saw. So some days I'd have 6-10+ chains to do each night in my shed after dinner. This would also be after a full days work followed by a clean down of my saws/bars with compressed air and any little tune ups needed to prepare the gear for the next day like topping off fuel and oil, greasing nose sprockets, cleaning air filters, dressing rails etc. You could rush it and do it in 20mins but often 1/2 an hour was needed blasting saw chips soaked in canola out of bar rails, floppy caps & clutch covers into your face, clothes, hair I wore plastic glasses so eyes were on occaision. I became good at hand filing, I had no option, after all an hour or so practice each day doing anything improves your skill & muscle memory. Then one day my father sent me a package with a new grinder in it, I left it in the box for weeks as I had not ground before and could hand file well. But then one weekend I set it up and began the journey of mastering the new machine. I was pretty average initially but I soon realised some distinct advantages the grinder had like a vice with 0-35° scale under it that held your chain dead accurate cutter after cutter. Despite the strength your hands & fingers get filing 5+ days a week, it seemed rather neat to pull a spinning wheel into chain teeth powered by a motor. Now days having around 150 loops of chain in circulation between all the bar sizes and saws I use its so fast for me to do chains now after work. Filing would really relax me, no one was there, it was just me time and I enjoyed it. But now its the same except I grind and spend a fraction of the time per chain. I've never sharpened chains in the field, the work is tough enough, I just swap out chains as I go having a minimum of 3 but as many as 6 chains per tool depending on what's going on. I still by files by the dozen & occaisionally file a chain by hand. My skills and natural instinct has faded quite a bit compared to what it used to be. My hands tire much faster now and I'd kinda dread going back to hand filing every day, my hands hurt thinking about it but I enjoy doing the odd chain now & then. Work chains are just that, they need to perform and be smooth on you and your gear, I've never put a stopwatch to a chain I've sharpened but I've done a few & found what works for me.