If it were just a matter of pure DPS, I'd stick with hunter. But with shammy, you get similar DPS plus:

  • AFK group disease/poison cleanse
  • fire/frost/nature resist
  • wipe prevention
  • 30% DPS boost every 10 minutes (or sooner if you wipe shortly afterward :P)
  • Fear reduction to 3-sec max

Much more than you get from a hunter. Especially if your group is mostly magic damage as hunters primarily benefit physical damage classes.