S/Y Fiji Siren
I was on the Fiji Siren in Feb. 2014 and loved it! The Nai'a is also an excellent choice but there are some differences between the two, and I think I would give Siren the slight edge, though my reasons for doing so may be different from what you're looking for.
Cabins: The cabins on the Fiji Siren are really nice and have more floor space than most liveaboards I've been on. I really like the wood floors vs. having carpet which inevitably ends up smelling like mildew. The mattresses are comfortable, and the bathrooms are nice as well. The only complaint I have is because it's all wood, it sounds creaky at night.
Food: Yum! I have a pretty restrictive food allergy, and it was well catered to. All the ingredients seemed very fresh. Fiji Siren offers all meals buffet style, which I prefer because it means you can have as much or as little as you want, and can eat it in the order in which you prefer, instead of waiting for individual courses to come out.
The Boat: This is where I really prefer the Siren to the alternatives. The Siren has a wonderful outdoor dining area with really nice lighting above. The indoor lounge is very spacious, and each guest has personal drawers for storage, not only in the galley but also on the dive deck. Speaking of, each guest has their own dive area with their tank, gear, and a few drawers to store stuff like hats, sunglasses, etc. It's a well laid-out boat with nice lighting, and it feels warm and cozy.
Guides and diving - Awesome!
Fiji is one of my favorite places to dive, and I'd recommend the Siren without hesitation!
