This is like saying "who would win? Chuck Norris or Steven Segal?"
Easy, neither, not even Gordon Freeman or Master Chief, they are all weaklings. Pit Chuck Norris, Steven Segal, Arnold Schwarzenegger, Sylvester Stallone, Gordon Freeman, and Master Chief all together in a fight, none will win, all will die, because Duke Nukem will show up and kick their collective asses.