I like LC M-80, and IMI M-80; mainly for the brass to reload. USGI (including LC) and IMI each use a heavier brass configuration. None of the M-80 loads are intended to deliver peak accuracy; their intent is for fire suppression during maneuver warfare. This is why the services have separate Sniper/Match loads like M-855, etc. To me, this is not a big deal, since I consider the M-80 loading as an area denial item, and not a Match load.
LC and IMI are comparable, and IMI may be preferable, by a squeek.
PMC is made in Korea. Not a downgrade by any means, but my experience was that while I got some exceptional performance out of some of the PMC, I also got not-so-exceptional performance out of other, identical boxes of it.
My overall preference is for IMI because it and LC have the better brass; and that brass is specifically designed to tolerate the utterly brutal extraction operation of the M14/M1A. No other Semi treats fired brass as badly, which is why the US NATA cartridge case is a much beefier animal. For all intents and purposes LC and IMI can be treated as identical. The IMI Semi-Auto Match 168 is my 20" PA-10's favorite load.
But in any military case, even LC and IMI, have a 3 reloadings limit on them.
To answer your initial question, I would prefer the LC over the PMC.
Military handload recipes should not be used in commercial brass (Rem, Win, Fed, etc.) without at least a 1gr reduction in charge weight, despite the increased capacity in commercial brass..
Before anyone gets the idea I'm dissing these things, I state that I am simply paraphrasing Glenn Zediker, who literally wrote the book on reloading for the M-14. I worship at his feet on this subject.
I am currently working up a large batch of M-80 on my press, and all the cases will be IMI. The second batch will be made to M-855 specs.
Greg