Cored hulls are lighter, stiffer and often stronger than solid laminates (they also offer better insulation in colder climates). It is true that they might be more fragile than solid fiberglass if thrown up on a reef or similar, but that is not what you build boats for. It is considered kind of outside the design envelope <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
I suspect the surveyor you have been reading about is yearning for past ages.. Look at the most extreme boats and how they are designed and you will find sandwich laminates. The same is true for mass produced boats and modern aircraft parts. In short, cored composites are here to stay and when done right they are both long lasting and better in all ways than solid fiberglass or traditional wooden boats (some of the woodies are quite amazing even by todays standards. Both traditional boats/spars and epoxy/wood construction). If you want some good PR for wood/epoxy, try to get your hands on the Gougeon book.