A fish form kayak may have a slightly blunter entry but will have a more slender exit through the water which increases tracking, even in adverse conditions. The actual performance of the kayak will be determined by the waterline shape, not the deck shape. The cross section gives the initial feel of the kayak. A round hull is extremely fast but very unstable where a flat hull is initially stable but very slow. Flared sides give comfortable secondary stability because of added buoyancy when leaning to the side.
Many kayaks have a shallow V hull with slightly flared sides.
One specialized Current Designs kayak, the Expedition, has a rounded V which is very fast but will feel more stable with some gear or ballast in it. A V hull shape gives structural rigidity to the hull, excellent tracking, a lively feel and a very comfortable level of stability. A hard chine kayak has a well defined turn where the V comes up to the side. This hard chine gives a unique feel to a kayak giving very good stability even in a narrow craft. Kayak manufacturers choose the most appropriate shapes for the right combination of tracking ability, speed, agility and seaworthiness depending on what the kayak was designed for.