Wouldn't you push it too?
And I don't push a cored hull, please don't toss me in with the rest of them.
The argument has always been that it makes for a "light" hull. I have yet to have found a scale with "light" somewhere on the dial. You are replacing layers of fiberglass for either foam or balsa core, or in some instances a honeycomb (either resin impregnated kraft paper or the material from recycled milk bottles to which resin doesn't stick) so you're saving the weight from the layers of fiberglass themselves and also the resin it takes to wet those layers of fiberglass out. However, you're shoving in blue/green/pink/white goo to bed the core into, you're adding resin to the product to seal up the kerfs and eliminate voids, and then you're adding the product itself. Go pick up a box of core, I don't care what it's made of, and tell me it's "light". In some instances, say a pilot house for example, using a core gives you a thicker product quickly and for how it is constructed it is a stiffer laminate than if one just used the total number of layers of glass. For example if one used the simple layup of gelcoat, 2 layers of 1.5 oz mat, 3 layers of 1808, 1.5 oz mat, and made a panel - let it cure and then propped it up on some blocking and stood on it, it would probably have a real swell curve to it and result in cracked gelcoat. Now if we tossed in some 12 mm foam core bedded into a super wet layer of 1.5 oz mat right after that first layer of 1808 and kept the rest of the layup schedule the same, let that cure, propped it up and stood on it... It wouldn't flex nearly as much. However, that panel will be noticeably heavier than the solid glass one. And a pain in the ass to repair if punctured - due to the reason that instead of penetrating in a localized spot, the core has a tendency to morph and carry the force along a longer area. Kind of like the fat kid doing a cannon ball in the pool. Effects a much larger area than if they did a pencil dive.
However, if one is making a solid laminate 3/4" thick from just glass alone, it would be tremendously overweight in comparison to the one with 12mm core. But a lot stronger too. If you have enough internal support one doesn't have to worry about hull flexing at all. You really think some plastic foam the thickness of the diameter of a dime will stop the force of the sea when you crest a 15' wave as you're heading into the wind and you fall though that open space and land into the next wave? It's your stringer system that distributes that load of pressure.
Boils down to how much you get caught up when being sold product, core is not snake oil by any means, and one should consider how they are going to use their vessel. If it is going to be sitting at the slip 99% of the time for mai tais and act like a floating porch, sure go with a core, it's not like you're going to be using a down east boat for the way it was intended to be run. But if you want to be able to go out, regardless of the weather, and come back home - go solid glass. You're wife will be glad you did.
And I know some of you reading this are going to pipe up by saying "but you just said to use it on the topsides, what gives?" Well chances are you won't be hitting any rocks or pilings from days gone by with your super structure. But if you are, you're upside down, and you have a whole other list of troubles. The super structure is there to keep the water off you - not to keep the water out. Consider that.