Anti-sway: truck option or hitch option or both?

I have a 2011 GMC 3500HD Duramax with a factory installed stability control system specifically designed to control trailer sway. It uses both the truck brakes and the trailer brakes to reduce sway. It also manages engine speed and gear selection. I pull a FC25FB. I have a weight distribution hitch but no anti-sway attachment. The trailer maxs at 7300 lbs with a 830 lb tongue weight. The truck is rated for 1000 lb tongue weight and 13000 lb trailer so it will pull the trailer without a WD. I want to know if adding anti-sway bars to the hitch gains anything for me. Am I just adding redundancy to the truck stability controller?