The main choice is between fins with straps or with a full feet enclosure.
In warm waters I favour the latter, wearing very thin "neoprene socks", inexpensive protective devices keeping the feet safe from abrasion due to sand between rubber and skin.
If you wear a thin hydrodynamic suit, or even no suit at all (at Maldives you do not really to use any), and you use a single small-size bottle (10 or 12 liters) and a tiny back BCD, you are almost as hydrodynamic as a free diver. That's the reason for which I always employed free-diving fins, such as Cressi Gara (not the longest ones, indeed). They are great in strong currents (a pass at Maldives can have more current than a river), and for jumping on the Dhoni without waiting for the ladder to be free.
But everyone's legs and ankles are different, demanding for different length, stiffness and angle between the shoe and fin. You should test many and find the ones which are perfect for you. And you have to learn the optimal pace and aperture of kicking for your fins. Many people simply do not take care of optimizing the matching between legs and fins, choosing them for aesthetics or for other considerations, while I think that this is something deserving great attention, because it can make diving much more safe and definitely more fun, with less fatigue and larger range of exploration.