Stuart, the platforms are so equal its scary . I feel the new sail designs are superior, and the wing mast probably has an advantage, but my bet is the same guys would have won the NA's on any boat there. The good sailors "happened" to be on new boats, but its the talent in this class that determines finishes. At spring fever Nigel and Dave Ingram switched boats, and Nigel and Alex still kicked everyones butt by the same margin(alot).
Bottome line...
Tiger, Cap, NACRA(any year other than I18) with new sails, are head to head equal around the cans. Distance is yet to be determined, but you need to be on an I20 if you are going distance racing (in the Atlantic anyway).
And I hate to say this, but the F16 is a cool little boat, class is in its infancy here in the states, but will probably grow, although I doubt it will grow as fast or as big as the F18 class because the Tiger one design was already established and was encompassed into the class.
Just my opinion, flame away!