Lets take a look at each hero on both teams, and see who they can defeat on the opposing team.
Iron Man defeats: Batman.
Batman defeats: Captain America, Wasp, Ant-man.
Superman defeats: Iron Man, Thor, Ant-man, Wasp, Hulk, Captain America.
Thor defeats: Batman, Aquaman, Wonder Woman, Green Lantern.
The Flash defeats: Captain America, Iron Man, Wasp, Ant-man, Hulk, Thor.
Wonder Woman defeats: Captain America, Wasp, Ant-man, Iron Man, Hulk.
So far it will be more victories for League members against Avengers members although I prefer the Earth's Mightiest heroes