A WD and anti-sway set up will make a big difference. I use both when towing my X-250BHs. I have yet to notice any sway and i routinely roll along at 65-70mph.
A X189 will be easier to tow but you would still get some sway most likely.
Even though these are light weight trailers, imo, a person still wants weight distribution and anti-sway for the 18'+ models when towing with a 1/2 ton truck. It will make for a smoother, more controlled and safer ride for the passengers. Plus you will take care of your sway problem.
Get the trailer you really want and spend the little bit more for the added safety it gives you.
'09 F-350 6.4l Crew Cab
'10 Komfort Trailblazer T262BSLE