Should I use a Dremel or a file to sharpen a chainsaw chain?

A file is better. A Dremel is less precise because it spins fast and makes it easy to remove too much metal or mess up the angle. With a file, you feel and see the cut. If you already have a Dremel and just need a quick touch-up, it works, but for regular sharpening, buy a cheap file guide. Don’t use a Dremel on a brand-new chain.