Dunno I like both of them.
Garrosh's horde is more like I wanted this expac to be. Not quite as brutal as id like the horde to be but closer.
Being the "bad" guy, why not. It suits me fine.
My view of how the horde should be fits more If the horde came to pandaria commited genocide on innocent pandarens, enslaved the survivors shipped them back to orgimmar and so on. Essentially making the entirety of the panda race the new peons.
The whole pandaren joining the horde, I would solve like so; they could be the traitors of the slaves (slave overseers, perfectly normal to use the captives to control themselves they had them in Auschwitz).
Then we could actually have an expansion focused on the war between the horde and alliance and not against some outside threat.