Island to recommend other than Tanna and Efate?

Hi there,

I'll spend 2 weeks in Vanuatu in October. I'll spend 4 days in Tanna and a couple of days in Efate of course. But I'd like to visit another island and just can't decide which one. I like hiking, snorkelling and volcanoes. I thought first of hiking up Ambryn, but after reading the LP, I'm not sure about it. I'm thinking about Epi, with its nice view of Ambryn and Lopevi, but I wonder if another more "exotic" island would better fill my curiosity.