Like the JawHorse you are able to operate this tool hands free. I don't know about you but a couple of times a month I find myself one hand short when I am trying to set something in my vise and get it level or square.
Clamping a work piece into place so that it can be drilled or sanded can sometimes be a pain, especially if the work piece is small or an odd ball shape. While I have a traditional carpenters vise,
I can certainly see an application for a tool like the Bench Jaw.