As a hunter you can have about 3 pets (two stabled one you use).

So you could have a pets of different types, and swap in and out as necessary (although probably more of a pain whilst levelling).

I levelled with cats till outland then got a ravager.

I should have tried more pets. Owls are meant to be really good for holding aggro as are boars.

So I would probably level with boars as the owl screeching is annoying. Then get a ravager for outlands. (they are a good dps pet)