the difference with this set up from Cole Tac is you can remove the straps and put it on a different bag. it just happens to come with this bag.
the other bags mentioned have the clamp BUILT IN.
the cole tac is nice because you can just take the straps off and use your bag as normal if you don't want the clamp for that particular stage.
this was JUST released yesterday. i'm sure no one has played with it except a select few.
i think it's a great idea