Open fins are nice for all around use. Shore dive, boats, etc. It gives additional protection from dropped weight belts on boat benches, protect your feet and give you better tractions on the boats, and simply nice to use around the pools.
Advantages of full foot fins is it is light to travel with. Disadvantages, is some with irritate your heel, the side of the ankles, and it is hard to get one that fits perfectly. I find divers putting tapes on these sore spots, then you might as well dive with open heels and boots.
Further advantages of open heel and boots is in heavy current and you are clinging on a trailing line, the foot strap and fit around your forearm and you can still hang on with that same arm while removing the second fin with your free hand. Then you can slip both fin straps on the same arm, and climb up the ladder or hand them to the boat hand. It is harder to do with full foot fin, and I've lost a fin just because of rough sea.
Walking around with boots keep athlete foot fungus from infecting your feet, important to think about when you get older and more prone to jock itch, athlete foot, and toe nail fungus.