Deciding between Batman and Superman is definitely a hard call. On the one hand, it's very clear that it will be Batman who is forming the Justice League in the DCEU (with help from Wonder Woman), and his talent as a strategist coupled with his vast experience makes him a natural choice to lead. That being said, Superman is the most powerful hero on the team, and he provides a much better face for the organization -- which goes a long way towards establishing public trust in the Justice League. There's no clear-cut answer here, but we have a feeling that they will eventually figure something out. They'll have to. Steppenwolf is coming and he's not going to wait around while they try to figure out the minor details of the team.