I say Fiji because it's my favorite region for kavas.Honestly, six weeks wasn't near enough time to see all the places I did. Felt like I was always on the move. If you've only got a week or two, sticking to one, maybe two countries is the way to go. Fiji is definitely the most traveler friendly with regards to flights, accommodation, and infrastructure. They're all beautiful and vastly different from each other though and have their own individual charms, of course.