Maybe you can judge from these videos of the Lady Gaga vs Madonna fight on SNL.
Madonna and Lady Gaga SNL Redo Lady Gaga Madonna "Fight"
It was staged of course but Madonna seemed to be the more aggressive one my guess is she would have taken Lady Gaga in a real fight.
I also just saw where Lady Gaga and Carrie Underwood are both to be on the American Music Awards tomorrow. Now if we were guaranteed they would get into a catfight I would actually watch it. They say Carrie Underwood is channeling her inner Lady Gaga. How about if Lady Gaga channels her with some face slapping and hair pulling?