Impish or Adamant Gourgeist

Hello! I am playing Pokemon Y and got very lucky, hatching two female Pumpkaboos with beneficial natures, however, I cannot decide which one to use. One is Adamant, the other is Impish. If you can, please help me out! Thanks! :)

Impish would be better as Gourgeist is primarily a defensive pokemon and as such the nature should reflect that.