I'm really late to this party since I have only just recently (past 2 weeks) begun seriously entertaining a tire upgrade. I read all 75 pages of this thread and there is some really good insight... and some that has me really fighting the urge to be contrary.
"Unsprung weight" (i.e. heavier wheels/tires) and their impact on vehicle performance (ride quality, braking distance, acceleration, suspension behavior) is thrown around in almost every corner of automotive/ATV/UTV/cycling enthusiast forums. The idea that this is the line in the sand for some people is such a head scratcher for me. I'm not an automotive engineer, but I am an engineer with a (half) mechanical focus. I understand the concept, and I am NOT going to sit here and say that it isn't a valid variable. But, it's just one variable in a system of systems that each have their own variables, and then cumulative variables in how they integrate and interoperate.
This is a 5,400lb truck... there is no way that I am going to believe that an additional 10lbs of "unsprung" weight on the corners (thinking SL vs. E load in general terms), even if dealing with rotational axis forces, is going to have a significant impact on performance. Hell, it isn't going to have a huge impact on MPG outside of situations requiring persistent periods of acceleration. What will have an impact? Those stiffer sidewalls forcing the suspension to further compensate. Those aftermarket, retro-styled wheels with weight distribution further away from the axis. Running tires at lower than required pressures because your E-load is too bouncy, creating more surface contact, and thus more friction to overcome driving down the road.
My other toy is a Polaris Ranger 1000XP crew cab. I have added about 15lbs of "unsprung" weight to the corners of that thing, and I understand the impact that can have on the whole system of systems. Even with a much more significant ratio of unsprung/sprung weight change (the vehicle weighs about 2100lbs full of gas), the impacts of that weight are only barely noticeable. Mainly, it's slower to get to speed.
Y'all are mostly pretty awesome, and I hope you don't judge me too much for failing to resist the urge to be contrary. But, after years of overland modding 4Rs, Tacos and Jeeps, 40 total pounds of additional unsprung weight is the very least of what informs my decisions. The stiff as a board, 10-ply sidewalls, however, are at the top.