John - I think I would disagree with you regarding the propensity of "composite" foam to dent.

When glass covered with proper weight cloth and properly epoxied to foam on both sides, unless you bash a rock or use only one layer of glass cloth - I feel the foam would work as a composite - just as wood does. If glass delaminates from the foam core, it probably wasn't a very good layup.

Too many boats use foam cores - for hulls, decks and even internal bulkheads where veneer is used for surfaces as well as glass. Foam will break down from UV exposure just as epoxy resin will. And should one suffer a ding that really does cause delamination - a router, ... some more foam - or just filler, ... and cloth will be a lot faster and easier fix than a wood strip core. Since a foam composite hull will probably be painted (not too many good looking pink or blue boats) but a wooden boat will usually be clear finished and varnished - which is easier to fix? And if the wood boat happens to be of thin 3 or 4 mm plywood S&G panels instead of 1/4 inch strip - then that becomes even more of a factor than repairing strips. The thicker the core, the easier to patch (in my opinion) as you only need remove the glass in the immediate area, add some filler and reglass and repaint. No need to cut out a strip, fit in a new strip and try to get a color match with varnish and epoxy after the wood around the repair has taken on a different color due to exposure to weather.

If you are concerned about foam denting - then look to Airexx or other high density foams instead of housing insulation types. They will be special order, will cost more, but be much more dense (dent resistant) than the light-weight blue or pink home repair stuff.

As far as weight comparison - probably a section of 2 inch thick pink would weigh close to the weight of similar area of wood and cloth composite. (just a guess)