Expect the weaponry to be more futuristic. Units can now gain veteran status, allowing them to move faster and become more resilient to damage. The new features added to game play are what really stand out. First there is better interaction with the environment. Maps are fully three-dimensional allowing for bridges and tunnels where units can pass over others.
Attacks can come from land, water, air and even subterranean units.
In addition, the environment is interactive. Heavy artillery can destroy bridges, which your engineers must rebuild. Bombs and rockets cause craters to be formed in dirt, which are gradually eroded away. Explosions cause brushfires that mask troop movement. Ice cracks and breaks beneath the footsteps of giant mechanized walkers and tanks and refreezes given time.