where to go?

Hi, I had to change all my plans, but it seems, that I will finaly go to Tonga for 10 days top, in june or july. I need your advice if you may....

I am in doubt between Haapai and Vavau.... I wanna go to a scenic place, and dive a lot, but still stay cheap and be able to walk around and meet locals. I am crazy about diving and I heard that Vavau is the place, although Haapai is more deserted and wild... Can you give me advices on where to go/stay? I'd like reccomendations for staying on a budget place in Vavau (since I have some for Haapai). Also, the oopinion of the best dive operators in that group! Thanks a lot in advance!