We have a 1 ton and I've pulled our 30' Airstream both on the ball and with the Propride. Never would I pull without anti-sway, given the choice. The different between with and without is nearly terrifying and all it takes is one time for the amplitude of the sway to exceed the ability of the tow vehicle to counter it and you have a disaster. Swerving to miss a deer or an accident, strong crosswinds combined with the pressure wave of a passing semi, etc.
You'll get anti-sway religion when you see enough trailer sway accidents, we've certainly seen our share.