This all really goes to show that there is no substitute for 1) learning how to read a tire's sidewall info; and 2) actually spending the time and effort to shop around, which should include any performance comparisons you can find online or in good magazines.
Recapping (no pun intended) some of the great info so far:
Generally, the higher the load rating, the stiffer the sidewall and the firmer the ride. But that works well on our heavy diesels. And load ratings vary even among identical tire models with even slightly different sizing.
Tires with lots of siping are great on wet or icy roads, but won't live long on rocks and gravel or perform as well in mud.
When shopping for mud-tread tires, I generally look for staggered or asymetrical tread blocks or lugs, as opposed to those with rows of one continuous pattern. They bite and self-clean better and, in the case of the BFG Mud Terrains at least, have also been designed to lower road noise by cancelling or interupting harmonics.
The one important thing I don't think can be found on any sidewall is rubber hardness or wear info. That's a darn shame, too. For that, I think you have to talk to people who have owned them or, like I have done too many times, buy them and learn the hard way. The best "budget tire" I ever had on a 4x4 were Wild Country radial mud tires. They look and perform very much like BFG's and wear great. But my tire guy tells me they changed the rubber compound some years back and that they don't wear quite as good now as they used to.
I think the construction of the carcass is the single most important factor affecting how a tire wears. Stronger and stiffer tends to wear better in my experience, with Michelins, which I personally find to feel almost mushy, being the one notable exception. They tend to wear a long time on pavement. On my semi, I like them as drive tires, but can't stand them on the steer axle due to how much more the truck leans in corners. I also run my tires at max-inflation levels for optimum wear, load capacity, and fuel mileage.
I've never owned any of the newer 17, 18, or 20 inch wheels and tires. It is interesting to hear that the decreased sidewall height can lessen the load capacity. I never considered that, but it makes sense. It's obvious that they sure can't provide the shock absorbtion that the taller sidewall of the same diameter tire on a smaller diameter wheel can.
It's one more thing to compare when shopping for tires, which is a very important and significant investment.
I've found this thread very useful. Lots of good info and opinions here. Like one old motocross racer once told my son at the track while giving his approval of my boy's super gnarly new knobby: "The next best thing to a brand-new bike is a brand-new back tire. " The same holds true for truck tires IMO. Tires can change your truck's entire attitude.