RE: Is it necessary and what is/are the advantage(s)?
Anything that adds to the killing effectiveness of the head with out sacrificing the ability to put the head where it needs to be is a good thing. You can't regulate stupidity. Unless its blatantly false advertising, you can't blame a broadhead manufacturer that makes a perfect fine and very lethal head, when someone doesn't use it under the correct situation. I believe I would have found a couple deer a little faster had they been hit with a huge cutting head, but I am not willing to trade my confidence in the head I do use for when I hit bone. If I have to trail the deer 40 yds or 70 yds, I am still going to find a dead deer.