Not sure, but I think Hallberg-Rassy?? I do know they also use a grid system and think it is a hand laid solid GRP.
HR is a foam sandwich above waterline. They call it insulation, to avoid all bad publicity
Nauticat is all fiberglass, there is no sandwich anywhere, not even in a deck.
1. Either stronger at same weight or lighter at same strength
2. Rigid, less or no flex
3. Better insulation, both thermal and acoustic, no running water from sides, warmer boat.
4. Lesser internal structure. It is easier to customize interior since it doesn't depends on internal structure of a boat as much as true fiberglass boat's interior.
In about every aspect, sandwich is better material, as long as it stays whole.
Talking from experience here, I already recored about 1/3 of my boat