Where are you located, and which fleet will you be racing with? If you are in an area with a Hobie 16 fleet, get that. If you will be racing in a mixed fleet, with no Hobie 16's to race against, you may want the Nacra 500. The Hobie 16 is still one of the largest classes racing, so your chances of finding some of them to race with are much greater than with the Nacra 500, of which there will be very few to race boat to boat.