To borrow from Rumil:
In my view orcs can be organised like this-
1a- snagas, mountain maggots, 'The Hobbit' goblins -small orcs
1b- everyday orcs, Grishnakh's company, majority of Mordor orcs - medium orcs
1c- Uruks or Uruk-hai of Mordor - big orcs
1d- Uruk-Hai of Isengard - various shades of mixture of orc and Men
1e- Halforcs that are obviously orcish
1f- Halforcs that could be mistaken for men
1d through 1f are all Saruman's specialty.
Also, eating man-flesh is no distinguisher of orcishness; cannibals eat man-flesh and they're men.
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