The Mini comparison tool lets you easily view the stats of two different troops side-by-side as well as the same Hero at different levels. It also describes the traits of each unit and automatically calculates which one could KO the other faster.
It's a quick way to get a good sense of which Minis counter each other and to learn more about different matchups. To use the tool, just select each troop you'd like to compare above. If you want to compare them leveled up, you can slide their level bar and see the difference between each stat according to the green numbers.