When Australia II won the America's Cup in 1983 winged keels became all the rage. There can be some advantage in increased efficiency but that is really only an advantage if you are limited in draft. Since the old 12 meter rule has a chain girth measurement in the formula adding wings instead of draft is a bit of an advantage. Pure racing boats did add wings on bulbs for a while but increasing the draft, making a longer thinner keel does the same thing but also helps get weight lower. A wing seems to be an attempt to regain some performance when creating a shoal draft keel. The problem is it can make getting free of a grounding much harder. There is a thread with great input from Jeff H (probably Jeff Halpern that used to contribute to this board) here http://www.sailnet.com/forums/general-discussion-sailing-related/9751-wing-vs-fin-keel.html