Difference between harness grip and seatbelt grip?

[WhiteShark]

IS there a functional difference between these two grips? I can see the mechanical difference like hand positioning etc but are they used for different things? The pressure seems so similar that I'd guess they are interchangeable. Does anyone like one over the other a lot?

Harness in beginning of this clip:
http://davidavellan.com/one-arm-choke/


Seatbelt grip here:

[mrh80]

To me they seem the same, the emphasis is to keep your chest tight to his back and your head tight to his; I prefer marcello's hand grip. Another variation I have seen is where you use your shoulder behind his head and overhook arm in front to really lock his head in place and that allows you to move your head away slightly. In this case the hands slide up higher towards his shoulder and is more useful if the opponent starts to slide away.

From what I have read online the Ryan Hall back attack dvds go into great detail with the harness grip for controlling the back before getting any hooks in.