Gree: I think there is love all around <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />
I was helping out with the I-14 Worlds and was impressed by the speeds they take those things downwind in a blow. If you think you are using them for marks when the wind is up at 18 knots, I would say you have to catch them first. That was the I-14 and the Aussie 18 are faster.
I think around the course, with wind, the Formula 18 would win. That is only because of the upwind though. Maybe just barely, or not, over the Aussie 18.
Dan