The IWCA uses a different set of class rules - the primary difference is they allow non-OEM sails, which inflates the cost of competition. A racing sail for the Wave can be very expensive.
Well, ... I race in both NAHCA and IWCA regattas, and an aftermarket sail for a Wave, mine is a North from the Bossett loft in New Jersey, is only a couple of bucks different in price than a new white sail from Hobie. The Hobie colored sails are more expensive. It would appear that the aftermarket sails might be a touch faster as well, judging from regattas where both raced together. Since sails do get used up if you care about performance then it's a question of design and longevity. I have an opinion on that but it's just an opinion.