I think you have to recognize there are 2 different types of conversion.
The one pictured just uses serpentine belts. But is a multi belt conversion.
Jerry's uses a single belt like the modern motors do.

The main reason for either is the dual belt a/c systems have issues today, finding 2 belts the same size, where one doesn't flap around while the other is already tight. Less slip etc..

Jerry's has the advantage of a single belt running it all. Not having to pull 2 belts to get to the one you want to change etc..

Of course the standard argument applys. isn't more belts better because even if you lose one, you could still be running with 1 belt etc..

I have always prefered the 1 belt and 1 spare from the last change anyway. now instead of a pile of them in the trunk I only need 1.