Advantages of reverse vang are:
That the crew has more space to work the boat. Not applicable for one man boat.
That the boom can be lower to the deck. not needed when the boom is as high as a moth above the deck.
Also it really destroys the shape of the lower mainsail, which does not matter so much with sloop rig as that area is so flat and sheeted close behind the jib, but on cat rig especially in mod to light wind this is the power area and a strut through the middle of it would really mess it up.