Hero Units offer a varied experience in Halo Wars' multiplayer aspects, bringing leader specific powers into the fray. The Covenant have a leader for each faction (Prophet, Arbiter and Brute) while the UNSC leaders function differently. The powers of the UNSC vary greatly and are numerous as opposed to Covenant leader units.
In campaign, they also can be revived if they are killed in action, as long as the life bar is halfway full. The life bar automatically regenerates while the leader is knocked down. However, in Skirmish or multiplayer if they die they die for good and will have to be purchased again to be on the battlefield, though only Covenant Hero Units are present on the battlefield in Skirmish and multiplayer.
In the Halo Wars Demo, Captain Cutter is the only available hero unit for the UNSC and the Prophet of Regret is the only available hero unit for the Covenant.
Cutter's unique unit is the Elephant mobile base, and his unique upgrade transforms Marine squads into teams of Orbital Drop Shock Troopers. Once this upgrade has been researched, he gains the Hero Ability to hot-drop ODSTs from HEV's anywhere on the map for the cost of training one squad. His personal weapon is the Spirit of Fire's Magnetic Accelerator Cannon, fired directly into the surface of the planet. Also, all bases receive free upgrades; newly built bases are Stations, not Firebases, and the initial home base which would usually be a Station is a Fortress.
Forge's personal attack calls in a Shortsword Bomber to Carpet Bomb an area of his choosing, and his unique unit is the Cyclops exoskeleton. His unique upgrade changes Scorpion Tanks into Grizzly Battle tanks. In addition, all UNSC Supply Pads start out as Heavy Supply pads, saving the 100 resources used to build normal supply pads. In campaign mode, Forge is available as a unit, initially riding in a Gauss Warthog, and continuing on foot armed with an M90 shotgun if his ride is destroyed.
Anders' unique unit is the Gremlin, and her unique upgrade replaces Hornets with Hawk . In addition, all upgrades are 50% cheaper and require 25% less research time, apart from Cryo Bomb and Hawks which are 25% cheaper and require 25% less research time. Her personal weapon calls in a Shortsword bomber to drop a Cryo Bomb on her enemies, which does no damage but literally freezes units solid, preventing them from taking any action. In the campaign, Anders is available as a unit, primarily useful due to her Active Ability to repair vehicles, though in emergencies she is able to protect herself with an M6D pistol.
Regret can bring down a Cleansing Beam from his ship in orbit to cause massive damage to enemy structures and units, his special forces units are Elite Honor Guard, and he personally enters the battlefield on on his hover chair, which could be upgraded to have sentinel protectors and to truly fly.
The Arbiter has the advantage of his devastatingly powerful Rage attack, and can train Suicide Grunts using his zeal to complete his mission. His personal upgrades increases his damage, reflect incoming damage back to his attackers, and even give him a permanent Active camouflage field.
The Brute Chieftain wields a mighty gravity hammer in battle, and his Vortex ability can tear units to shreds. His special forces units are Brutes, who can be equipped with jump packs, and his army uses Brute Choppers instead of Ghosts.
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. Also, the UNSC Hero Units have a special upgrade, like the ODSTs with Cutter.
Against the AI on skirmish, their hero unit of choice impacts on their playstyle. For instance, Cutter is more "measured" while Forge's playstyle is quite aggressive.
However, Cutter is by far the most dangerous AI opponent to face in skirmish. The computer Cutter uses extraordinarily accurate MAC rounds that somehow are able to track your units. Also, Elephants are sent in waves usually with a massive amount of infantry and/or Spartan escort.