The Busa is heavier and not nearly as fun. The new GSXR1000 and new 10R are very comparable. I would recommend sitting on the 2 of them and see which one sits and feels better for you. The 10R has more grunt, more ram-air "howl" to it, and I think is more agressive for riding. The GSXR is going to be redesigned again next year keep in mind.
Send a pm to "snake" on the forum, he has ridden both.