At Kadavu (Dive Kadavu/Matana Resort), you meet more of the locals as there is a village next to the resort. The village chief is over everyday ( I think he gets free food and drink) and he is always in a good mood. Sunsets at the beach bar are nice. You get used to no electricty during certain periods fairly easily. I did pay for the extra to take a dive on the other side of the island and we were rewarded with several Manta's. The dive structures are much better on the windward side of the island. You get to know everyone at the resort - at least we did.. there were only 7 of us for a time. We adopted the names from Gilligan's island and played the roles - and they were a natural fit to some degree. It was a hoot. If I was home now, I would post a pic of the group but I am traveling and using a borrowed PC.
There are essentially no roads on Kadavu, transport is via boat. Its very much a 'back to nature' kind of experience, and we thought a rather nice one. All food is at the resort and it was satisfactory- nothing special - nothing bad.
They only do the Manta dive on certain days so ask in advance...they may not be going the days you are there. And I think they only go if there are enough signed up.
Here is a picture from 20 yds in front of our bure and turning left.
Sunset at Matana Resort
Taveuni (at rainbow reef) overall has better diving, I thought - not counting the Manta dive and the windward side of Kadavu. There is pavement and towns, electrity and restaurants. We stayed at Matei pt and Maravu. Maravu is high priced and a honeymoon place. We spent no time with others at the resort. Its not a dive related resort. Cocoview was more dive oriented. We liked Matei Pt area due to other things to do there. Several places to eat, all a walk away. Diving was a walk away but the company we used folded...not certain what dive company is there now, but I suspect there is one available. Local resorts would know via email.
If you do rainbow reef, many nice pics can be had during the 15 ft safety stop...if you are closest to the reef hook...but you have to manage taking one-handed photo's while 'blowing in the wind'.
safety stop photo at rainbow reef
There is a kindly woman that runs a cake/pastry shop near Matei pt. She is a former US resident. Its like going to visit your grandmother and she sits on the porch and visits with you. She is lovely. Here is a pic from her front porch.
Near Matei Pt
Garden Island Resort is dive oriented but not so close to everything else. A ~ $5-10 cab ride should be able to take you most places in 10 min or so. Nearly everyone there would be a diver and its closer to rainbow reef than Matei pt.
I would expect a fun dive oriented culture at GIR but never stayed there.
Glad we stayed at both islands. The feel is totally different. A lot depends on the kind of experience you want.
Hope that is some help.
PM me if you have more specific questions.
Dave