Heirlooms. 1 hand maces or 2 hand staff?
Tanking - 2H Staff
DPS - 2 Venerable masses
If you're planning on leveling a Rogue or Enh. Shammy, take the Masses. If you're planning on picking up a CatBear Druid, take the staff.
For levelling? It won't matter for tanking. One will not be better than the other.
The thing that was said here that does matter would be the relevance of what future classes you might level.
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