Why? Does the Falling Skies team have better special effects?
Better organization. The falling skies bunch is a mix of civilian and military with actual orders being followed and everyone who can fire a gun, carries one. They all follow the orders of a military leader but the second in command is a former reservist who can adjust the orders to fit the civilian parts of the group.
Both groups are traveling through hostile territory but only one (Falling skies) is sending out patrols to spot the enemy and find supplies. The Walking Dead group is getting picked off 1 by 1.