Although I am confident the Dunn grizzly is an excellent head, I don't have any hands on experience with them, but I do know a little about the concorde. I bought a few of the older uncoated head blanks, back when they were offered that way, and wore out a few files converting them to right wing single bevels. Good steel, take and hold a good edge, mount straight and spin very well, and never had a problem with the way they fly. That being said, never hunted with them because I prefer a wider broadhead than the Concorde or Grizzly.
Never had a problem sharpening single bevels. Work the beveled edge until you get a small burr the entire lenght of the head, then flip it over and , gently remove the burr. Then I usually flip it back over and drag it across an extra fine diamond stone a time or two, and it's a done deal.