Scout, or light armor, allows blazingly fast movement, but very low armor. Scouts are also very light, so they can stay in the air much longer than the others with the use of the jumpjets. Able to pilot any of the multitude of vehicles in the game, Scouts are also the sole users of sniper rifles. They are great for reconnaissance or evasionistic gameplay. Assault, or Medium armor, allows one more weapon to be carried than the Scout, for a total of four.
Assaults have more armor, but are heavier and move more slowly.
The Juggernaut, or Heavy armor, can carry five weapons, but moves incredibly slowly. Also, Juggernauts are the only of the three classes to be able to use the powerful Fusion Mortar, but cannot pilot any vehicles at all. Juggernauts are aimed specifically for stationary, turret-like gameplay. Each of the classes is perfectly balanced and incredibly different. Each has a strategy and play all its own.