Boom vang mechanical advantage question

[Brian J]

Over on another forum we've been having a lively discussion about how to determine the mechanical advantage of a boom vang. This link is to a pic of two different vang setups. The only difference between the two is the direction of the tackle is reversed. What is the mechanical advantage produced by each?
http://photos.trailersailor.com/2004/block2.jpg

Thanks in advance!