When do you want or need a WDH and/or brake controller?

I have a 2010 F150 without tow package. I have a 4500 lb trailer. When I bought it, I asked the Dealer about a WD hitch and a anti sway bar. He replied, "why not try it first and see if you need it", I just got them, and have been happy, no sway when semis pass, etc. If you get it when you buy the trailer, you may be able to get a discount on it.