C-18 keel
I have a '93 wing keel C-18 and have not sailed a fin keeled version. As most (all?) of the C-18s built since about 1990 have had wing keels, I'd think the wing should provide better stability at speed. From looking at the keel design, I think the wing pulls the hull into the water at speed. This should have the effect of reducing heeling. A disadvantage of the wing keel is that they're a good anchor in soft mud (shallow water).