I'd say it also depends on how long you can stay. If you just stay in the Vavau group in northern Tonga you could easily do 1+ weeks and everything is really in a tight group of islands. Pretty pretty. But as NoTies says you may have trouble finding a
bareboat charter. There used to be a guy there but not sure if he is still there or not. Tonga officialdom was not very welcoming IMO. Very straight-laced. Not very good place for
provisioning. Neiafu was not our favorite place but nice and some good restaurants. The islands around Neiafu have been compared to the
San Juan Islands in the Pacific NW and I would agree.
Vanuatu was magical to us. By far our favorite place to
cruise. But distances are much farther between islands so much of your time could be spent on moving around. The people are wonderful. Smiles all the time. Excellent sense of
humor. Good
provisioning, good restaurants. We enjoyed our times in Port Vila but the other islands are the best part. Tanna Island is to the south, Ambryn and Pentecost to the north, lots of other places to drop the hook. You could easily spend 3 days at Tanna but it a long ways back past Port Vila to go up to Ambryn and Pentecost. And no charters that I know of but that was several years ago. The best kava that we found (if you care for that bitter, muddy high.) Many of the anchorages are exposed so you have to pay attention to
weather patterns and not get caught on a lee shore. Luganville is pretty protected farther north though and has interesting
history from WWII (as does Port Vila for that matter.)