Mules taste a lot like horse. I always found the meat had a slightly sweet taste, comparable to a beef round steak in texture and lean-ness. Mules are a bit more sinewy.

Oxen can get to have a bit of a wild taste if left to forage on their own. You can get mighty bowlegged riding an ox.

Llamas are good, but you can't ride them. Camels have too much attitude. Horses are generally less sensible in the bush than a mule, but tend to also have a better temperament and can go a lot faster.

I've seen pigs big enough to ride, but I don't reckon they would last long on the trail. Ever try to saddle a pig?