A few comments:
1. you're right, coremat is crap. They only use it because it's even cheaper than fiberglass (and ever so slightly lighter), but fundamentally it has no place in a high-performance laminate. Cheap powerboats, maybe. If you're looking at an entry-level ski, best to stick to one that's made simply from epoxy and fiberglass. Avoid polyester as well, unless it's the only thing you can afford. It's brittle and weak compared to epoxy.
2. Soric is a little better, as it adds more thickness to the laminate per unit weight, which makes the skin stiffer. However, it essentially forms an "epoxy resin honeycomb" due to the voids left in the core for the infusion path. While honeycomb is a great structural shape, making it out of plain epoxy resin gets you very little in the way of strength or stiffness compared to a real honeycomb core like Nomex.
3. Despite its widespread use in marine laminates, Kevlar is a PITA and I would never put it into anything that might have to be repaired someday. It simply cannot be properly feathered and repaired when the time comes. Plus, it's terrible in compressive strength, which means its use in the exterior of a sandwich laminate is almost pointless-- sure, it'll survive the impact without tearing a hole in the boat, but the matrix will still crack and then it has to be repaired once again. Which it can't be, at least not well.
4. Very few Mfr's are using prepreg at this point-- it is better than wet layup or infusion in every way, but also significantly more expensive and requires a lot more up-front investment in facility equipment (and re-training a workforce that is used to using wet layup techniques).
5. The ultimate construction generally will be full prepreg carbon, sandwich laminate cored with either Nomex honeycomb or one of the aerospace core foams such as Rohacell. No fiberglass, no Kevlar, just carbon and core. Nothing else comes close. But of course, it's also more expensive than what most everyone is doing these days. However, the high-end boats will all eventually converge to this, it's only a matter of time and learning.