Pele or Nguna?

My boyfriend and I will spend 2 weeks in Vanuatu in March. We've been doing some research and have decideded to go to Espirito Santo and Tanna. But I;d love to spend a few days on either Pele or Nguna as well.... But I can't seem to make up my mind abouth which island to choose (luxary problem, I know)! The time spent there will be for relaxation (and surfing if possible) only....

Any suggestions??