In my opinion Elemental Shamans has an easier time in killing pally due to pallys got hardly any range skills, kite (use frost shock and earthbind totem to make kiting easier XD) and spam lightning bolt lol but anyways if you have Elemental mastery and Natures Swiftness, cast both and do an instant Chain Lightning and hope for Lightning Overlord to proc XD

But Enhancment and Resotration can take down pallys so I'm not argueing which is the best :P