Neither. They would fight for 5 minutes, and realize that while Wakamoto was capable of destroying Araki completely with his other-worldly voice without breaking a sweat, Araki's immortality would cause him to keep regenerating infinitely. So, they would form a truce and go out for drinks. Soon, they would become great friends, and would make an agreement that should Araki ever produce any movie/OVA series for JoJo, Wakamoto would handle the voice for each character, as his is the only one capable of doing them justice.
And all would be right with the world.