Of course there will be naysayers for upgrading to LT tires from P or XL on a 1/2 ton.
Some reasons valid, like it's absolutely not necessary if you're hauling within the limits of the current tires.
Others pure conjecture, like ride quality. Stiffness of the tire and how it affects ride is about 99% the amount of pressure in the tire and 1% the load rating of the tire. Apples to apples size and tire model of course. Sure sidewalls are a bit stiffer, lower the psi a bit from what you were running in the light duty tires = same ride.
Loss of mileage is pure bs, apples to apples. If anything fuel mileage would go up a shade, but is likely indiscernable either way. Generally harder tread compound and that all encompassing "stiffer sidewall" makes for a tire that rolls easier. Regardless, tracking fuel mileage down to the penny and taking it for more than what it's worth, which is a good approximation only "if" you're tracking very accurately and attempting to account for every varied condition.
Example, been checking mileage and tracking on the odometer on one vehicle we have becasue the gas gauge is suspect. Been around 14-14.5mpg. Last tank, I filled, and checked was just over 15mpg. No surprise, except that the vehicle had slightly taller, slightly wider and considerably more aggressive tread than previously. And they're LT tires vs the Ps that were on it. Explanation? Nope. Seems it varies unless you're doing a carefully controlled test even though the vehicle was doing the same duty in general.
The advantage though, unless you're again, calculating $/mile of tire life down to the penny, is tire life. A lot of LT tires have greater tread depth than their P or XL rated versions of the same tire model and the tread compound is a little harder, which equals longer tire life.
Is it as much longer as the cost difference? Yes, no , maybe. Do you run your tires to exactly 3/32 and change them regardless of weather, driving conditions, Big O having a sale, etc? Probably not, but the fact that they last longer cannot be debated.