Proving who is better

Hi, I'm just another summoner who enjoys playing league. I have many friends of whom I play with constantly. As anyone would know in a large group, people are for lanes. In my group, we constantly bicker over who should mid. Me and one other player both want to mid as the same champion, Leblanc. I think that I'm that better player, but he thinks otherwise. I've come to the discussion threads here for help settling disputes. How would one prove that they are the better player at a champ?