Aw man, you just had to make this thread while I was making a thread about Rigid team structures vs. Non Rigid team structures didn't you?
I think it is a difference of Flexibility over Simplicity with Non rigid being more flexible and Rigid being more simple.
Our team uses a Non rigid system. How we do it is the leader will order the team to form up on an operator with the operator at the front of the formation being point man while whoever forms up at the back will be the rear guard.
I like doing it this way as I like to be more flexible with my team.
I guess birddog likes his way because everyone knows their position, hence the reason why I say it is more simple.