The Epic representative in Brazil, Guto Campos, is an accomplished paddler and has a lot of experience with surfskis. He told me that the ultra and elite constructions are virtually identical. According to him, the structural calculations in the design are exactly the same. The only reason why the elite is lighter than the ultra is because carbon is lighter than kevlar for the same strength. The honeycomb core is the same in both.
Still according to him, in the case of structural load beyond the boat's resistance limit, probably both constructions would failure at the exact same loads, that is, elite is NOT weaker than ultra in any way. The difference, he says, would be primarily the aspect of the failure: whereas the elite would show a clean, brittle failure, with parts breaking cleanly apart, the ultra would show broken parts probably still united by the kevlar fabric.
As to durability... Many people say that the seams are the weakest point in any surfski, and I tend to agree. I've heard (or read) that a super stiff construction like the elite would be too rough on the seams. Someone here compared a stiff surfski with a car without suspension. But again, I really don't believe that there is a big difference in stiffness between the ultra and elite constructions. They have the same core and the ultra has a good deal of carbon (kevlar inside, carbon outside the core). If you go to a "performance" construction (mostly fiberglass over a foam core) then yes, ok, you have considerable more flexibility.
Only time will tell, but I bet that the elite construction will prove to be as tough and durable as the ultra. The elite construction is admittedly prone to dentings and dings, as Robin Mousley pointed out, but again, I doubt that the elite is more sensitive than the ultra in this respect.
Current: Epic V8 PRO, Think Evo 3
Past: Epic V8, Epic V10 Sport