Wargs, IMO, should be rarer and better than horses in almost every way...
I don't agree that they should be better than Horses in every way, I will find it a damn shame if there is no point in horses after getting Wargs, especially with the dodgy system usually giving me Wargs before Horses.
So I think at least horses should be more easily accessible (A special level upgrade for fortresses?)
and meaby Wargs should have a backside to them, meaby they can still be knocked prone, or cant fight against spears.
If Wargs are just plain better, you might as well exclude Horses from the game and put in more Wargs, always had enough to build the mounted units I needed anyways.
@ Neborya, if the AI have very few Horses, but tons of Wargs ready, then usually they will sell Wargs cheaper than the few Horses they have, to maintain a steady balance between all they're resources.
Sincerely
~ Kongdej