On modern rigs, Tow/Haul does a myriad of things, including changing shift patterns, throttle response, in some even braking response and steering response (Fords adaptive steering) and more. It is very worth while to use while towing. One way to think of it is a built in push button tune. While it doesn't change your engine power output at all like a true tune, it changes a-lot of other things a tune would.
2016 Ford F150 XLT S-CREW Long Bed 3.5L EcoBoost.
2007 Jayco JayFlight 23FB