I think Jake kind of hits on what I've been thinking.
I've not been on an F18 in a while but I remember how nice the sails on the Tiger are. You know Hobie didn't make those sails, Ulman did. On the F18 if your sails suck, your boat might as well be garbage too. On the 20, there has been no other choice for sails... and no class competition to drive quality in both shape and construction.