I think the advantage of withdraw is the troops run right away. With move etc, they will continue shooting at the enemy before they move. If that is what you want them to get away from (the enemy), they will die before they get away.
Make sure your plot line is long enough for them to get to a resting place. They take a long time to recover and will have the "rattled" tag after.
Mortar and HMG troops will fall down tired before they reach that resting place so plan for that too.
It is a desperation order, if it doesn't work, you were doomed anyway.