there are also differences in the sail plan
the nacra 6.0, old school with pinhead main, big? roller furling jib, for better reaching?
http://www.google.com/sea…&tab=wi&biw=1024&bih=653
inter 20 with square top main, smaller jib but spin for better downwind etc.
http://www.google.com/sea…20&aq=f&aqi=g10&aql=&oq=