I got the 1h mace for my Elemental Shammy (I'm also working on a Priest atm). It has the same SP as the staff, but allows for a shield or offhand to be used as well.
But if you're planning on leveling a Warlock or Mage next, I'd get the staff as they can't use the mace.
Bear in mind that pre-58, they both have really lousy SP, so you'll want to enchant it (since you're going to use it for a really long time, it's worth dropping the 200+g for +30 SP).