We have a 2011 Suburban with 6.0L/6-spd/3.73. We towed two 2200 mile trips this year, plus our summer weekends. We aren't pushing the limits at around 7k loaded TT, but I comfortably tow at 70mph in 5th gear when not too hot and never below 3rd gear @60mph up any interstate mountain. It likes to spin. I budget 8mpg at that speed and get 7-9mpg depending on wind and hills. Otherwise, 65k miles in under 4 years. Two non towing trips to South Carolina, one Orlando trip, and lots of carting kids around town. It is our main family vehicle replacing a minivan and does everything we ask in luxury and comfort.
However, if I could get the pickup diesel powertrain in SUV form, I'd have that instead.