Aerodynamics?
The Busa's soap-bubble lines help its fuel economy and top speed. Round is better at subsonic speeds, and that is why the Busa has always out-performed the Kaw - even thought the Kaw has a power advantage. It's amazing how much wind resistance effects performance on motorcycles; and even more amazing how so many companies seem to ignore "Aeros."
Okay, aeros can be ugly - ie. the 94 series Saab, one of the most aerodynamic cars of its day (one the first cars ever to be designed in a wind tunnel) and ugly as a sea goat.