Originally Posted by
Super Dickmann
While it doesn't outright say they're slaves, they're a subjugated client race at best and it's obvious that this is ensured through force, with Kor'gall being a governor for them. The issue he takes with Geyarah later is that she can't protect them, which supports that interpretation. The quest chain is remarkably morally grey for how hamhanded some of the dialogue is.
While the MU orcs have been dead for quite a while that's largely because Blizzard cut out their development at the end of Mists along with most of their cast. The Mag'har have no cast except Geya'rah, but because of the clans they have a lot more potential for varied characters. They're also militant and industrialized, whereas you can focus on the more shamanic, repentant warrior shtick that Saurfang exemplifies with the MU orcs, coupled with Thrall's combination of Frostwolf and human society building. You can also have them clash over stuff like the use of the void, how they practice shamanism and industrialization. There's room to work with here and it's really a chance to nail down both as to what they're about and refresh the orc roster.