They don't have any real big advantages IMO. I have one because it gives me one less thing to mess with when hooking/unhooking the 5er. And the OEM tailgate was damaged when I bought the truck because the original owner forgot to lower the tailgate when he unhooked his gooseneck trailer. Also I don't have to worry about digging the corner of the tailgate into the 5er if I have to hook up at a severe angle. It's also easier for me to step on the bumper and into the truck through the tailgate rather than stepping over. Just personal preference I think.
I had mine powdercoated to match the truck and I think it turned out pretty nice:

I couldn't remember recommended image size. Sorry. :?