I have a 2015 durango citadel with a tow package which includes trailer sway control . I have an after market brake controller. I towing a 25 ft travel trailer dry weight 4500lbs. I want to know if I put a electronic sway control on the trailer will it be of any benefit . Will it work in conjunction with the Durango sway system

 

I don't know about electronic sway control on a trailer, but I can tell you that a weight distributing hitch with a friction sway control mechanism makes a world of difference.
My understanding of the system built into the Durango is that it is more of an emergency system to help you regain control in case of serious sway issues, not a mechanism to prevent it in the first place. From dodge: "Standard Trailer Sway Control14 applies brake pressure on alternating wheels and may adjust engine throttle to help eliminate sway and maintain vehicle and trailer system stability."