Difference between harness grip and seatbelt grip?

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: