There's an interesting point at the root of this discussion.
Scale models really do two things: they document the shapes of the prototypes, and they reproduce, in miniature, the impression that the prototypes make on the human eye. Most of the time those two functions co-exist without any problem. A well-made aircraft model, for instance, does both things well; the accurate shape of a P-51 doesn't conflict with the visual impression of it. (About the only difference I can think of between a "three-dimentional plan" of an airplane and the visual impression that it makes is that the visual impression includes the slight flattening of the tires where they touch the ground. Replicating that in a model doesn't interfere significantly with the accuracy of it.)
A ship is different. The actual shape of the ship obviously includes the hull below the waterline. But under normal circumstances we don't see that part; our visual impression of the ship is based entirely on how the part above the waterline looks. So the ship modeler - unlike the airplane or AFV modeler - has to chose between building a 100% accurate model of the prototype and a 100% accurate model of what it looks like under normal circumstances. As the posts above demonstrate, there are strong arguments on both sides.
Years ago I read an article in a British modeling magazine in which the (very well-qualified and knowledgable) auther asserted quite emphatically that full-hull models, except the enormous ones in museums, looked "utterly ridiculous." (He said full-hull models of sailing ships were ok, because the masts and rigging "balanced" the lower hulls.) As an example he pointed to Revell's Wind-class icebreaker kit; he said the characteristic bulged and bumpy shape of the underwater hull looked "perfectly absurd" in a model. I don't think the matter's that simple. To my notion that underwater hull shape is what makes the ship an icebreaker; if the purpose of the model is to demonstrate what an icebreaker is, cutting it off at the waterline damages its effectiveness. On the other hand, a diorama of an icebreaker shoving through an ice pack, with the model cut at the waterline, certainly would convey the "feel," and genuine appearance, of the ship more effectively. The same goes for a destroyer or a submarine.
Bottom line (as in so many other aspects of model building): to each his/her own. I suggest we refrain from asserting that one type of model is "better" than the other, and acknowledge that they're different. There's ample room for both - and nothing forces the modeler to pick one style or the other for every model. (My own tiny collection includes both types.) As for kits, I really like those that offer the modeler the choice of full-hull or waterline. Trumpeter, for instance, seems to be leaning increasingly in that direction with both its 1/700 and larger scale kits. Bravo Trumpeter.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.