I would prefer Lee Sin, but let's look at their pros and cons:
-Very high mobility
-Easy to escape with
-Janitor of the League (basically used to clean up the other team when they're low)
-Can be an off tank
-Pretty fast jungle time
-Pretty useful ult, kicking the enemy tank through its team is always satisfying.
-Is a great counter-jungler
-Is a safe jungler in general, especially against stealth junglers
-Decent sustain with W and wriggles.
-Isn't dependent on any buff in the jungle, and so can give blue away really early and red somewhat early.
-Energy regenerates really fast
-Doesn't require flash
-Can escape to a ward, so it's almost like a mini flash
-Damage isn't the highest
-His q is one of the most missed skill shots in the game
-Has a high skill cap
-Ult can backfire (to prevent this, use q, THEN ult then q again. This tip can still fail).
-Needs items in a timely manner or may find himself bursted into submission
-Can build tank and still do more than fairly decent damage
-Really fast jungle time
-Hard to take down
-Great slow with his axe
-Very great sustain
-Can be built off-tank depending on preference
-His ult gives cc immunity AND damage reduction
-Due to his passive and w, he has fairly decent attack speed attributes even early on
-VERY blue dependent. Without it you will find yourself jungling really, really, REALLY slowly and be almost unable to gank.
-Ganks require skill in q throwing. Missing gives the enemy a very high likelihood of escaping.
-Easy to forget your true damage ability damages yourself.
-Needs flash like almost everyone else
And there you have it. Both are great junglers and I would recommend getting good at both of them.