I learned this drag from the instructors at Prepare 4 Rescue (on Facebook).
I personally prefer feet 1st, leg drags. However, sometimes the occupant is laying head 1st towards the exit, or there isn’t enough space for me to get to their legs to spin them. This is the situation that I would use an arm bar drag.
The benefit of the arm bar drag is that the occupant’s arm is locked into yours. So if they are slippery, you won’t lose your grip.
The negative of the arm bar drag is it may be hard on your back. It’s hard to keep your back in an upright position during this drag, unlike the feet 1st drag. If I have to drag an occupant a large distance, I want to be doing a feet 1st drag.
This video includes my explanation of the drag.