I was torn between Xu-Fu and Chi-Chi as a first pet. Chi-Chi's self heals coupled with ethereal, the flying passive, and fire quills all just mesh together in a nice little kit. Xu-Fu on the other hand can heal his entire health pool as well as deal just as much damage at the same time. The moonfire + 80% hit claws are obscene damage and a great combo, but his prowl+feed combo is just so good it's hard to pass up.
I'll get Chi-Chi next. Then Zao.
Yu'la unfortunately is quite useless. Zao would've been a contender too if he had been a H/H breed with 1800-1900 HP. But with his really, really, really garbage stats he is pretty wasted. He doesn't have much power, and he has half his extra stats put into speed which cuts down on his power a lot but still doesn't give him enough speed to outspeed anything except the very slowest enemies. He has a horrible breed and health too low to really capitalize on wish. Zao would've been epic as H/H.