So, you have a shiny vintage PC, of the sort of era where it would run DOS (plus maybe Windows 1, 2, 3.x, GEM, PC-GEOS or Deskmate), and not Windows 9x, Windows NT, OS/2 or Unix. But it doesn't have an OS on it, and you're looking at WinworldPC and marveling at just how many different versions of DOS there actually were, and wondering which one is actually right for you.
TL;DR - Is there an actual definitive "best DOS"? No. PC DOS 2000, if you must have a quick answer, but even that comes with some caveats.
I'm going to ignore PTS-DOS, Wendin DOS, DOS Plus, Concurrent DOS, ROM-DOS and a few other variations because they're difficult to get, special-purpose, or mostly a curiosity. There's also the issue with licensing - to make a long story short, except for FreeDOS and certain limited parts of certain versions of DR DOS, all DOS is copyrighted software. It's mostly abandonware, so it's overwhelmingly likely that nobody
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