Are gyme has both, but I was told (I'm not sure how true it is) that the diamond one goes by a different name because of patient stuff. I dunno though. But I was told the the one with the dip is call a Trap Bar by name...the diamond has a name like Diamond Trap or Something to that effect.
we have something we call a trap bar, it's a rectangular bar about 2' X 3', with handles on the side i use it for traps because our db's only go up to 100's. it can also be used for squats, but if you put 45's on, you can't go down far enough