All three of them have very different jungle styles, so it's hard to compare them there. Maokai is great for ganks, Shyvana is great for farming and Lee Sin is somewhere between the two, but he's more difficult to play well. I personally don't like Maokai since he drops off quite steeply late game. Lee Sin is great if you can play him, not so great if you can't. Shyvana is the "safer" choice since she can simply farm/counterjungle so effectively she doesn't need to gamble on ganks.