Hunter, for sure. Mainly because you can kill while moving. I play both sham and hunt both of them have pretty much equal gear but my hunter is deffo doing things faster then my shaman.
The DPS on my hunter is also higher, not by that much but it's still higher, which means things die faster which makes it even quicker to finish things up.
You might think, shaman have ghost wolf so it runs faster but hunter have disengage, which also provides a speed buff, and aspect of the cheetah. As for the speed bonus i think their pretty equal, so the big difference is hunter being able to start the fight from a huge distance and you won't have to stand still and finish the kill you can continue pulling while your pet(s) finish them off as you press Kill Command.