All heavy infantry units are strong against ground vehicles and weak against defenses.
Heavy Weapon Squad
Heavy Weapon Squads are your Tier 1 heavy infantry. They have a moderate load capacity, but very low attack, defense, speed and health.
Pyro Squads are your Tier 2 heavy infantry. They have high load capacity but moderate attack, defense, speed and health.
Commando Squads are your Tier 3 heavy infantry. They have very load capacity, defense, and health, decent speed and power, and moderate attack.
Shock Troopers are your Tier 4 heavy infantry - the best heavy infantry you can produce. They have incredibly high health, defense, and power, as well as great load capacity and speed.