Leader

Background
Hero Units are UNSC and Covenant Combat Personnel in the upcoming game Halo Wars who are suited to lead Marine and Covenant ground forces along with air units such as Dropships, Hornets, Banshees, etc.

Known Hero Units
UNSC

John Forge

Spartan Alice

Covenant

Unknown Arbiter

Combat Experience
Being that they are 'hero units', they are more adept to fighting and have more armor for protection against the enemy fighting units. Along with that, they probably have more unique weaponry and have "special abilities" such as "Rage mode" for the Arbiter.