I love Thrall, I don't really understand where this 'Green Jesus' term comes from. There are plenty of people in the World that are stronger if not just as strong as him and yet people don't complain about them.
But Thrall is obviously just a choice. If we take at who they have at hand, Thrall would be the strongest leader. So unless the develop the other leaders, it's gotta be Thrall or it wouldn't make sense.