Definately compare the ratings and sidewall plies as well. Some tires come in an LT (C, D or E) load rating which means they have more/thicker carcasses/sidewalls compared to P-metric or SL rated tires. They will be more robust and stand up to abuse better and in many cases they have much deeper tread. Mud terrains and some all terrains also offer 3ply sidewalls instead of the typical 2. These tires are very puncture resistant and can handle being aired down very low yet still be durable. All of that durability and tread depth adds weight. And be aware that there is a difference between regular ply ratings that come with load ratings (C=6, D=8, E=10) and sidewall ply ratings. Assume all tires are 2ply rated for sidewalls unless stated otherwise or they are mud terrains which almost always offer 3plies. Generally speaking.
It's pretty amazing how much an aired down tire can fold when going through obstacles. You need a strong sidewall to avoid damage. This is an LT285/70/17 Wildpeak A/T3W at 15psi on a slanted rock. Times like this I wish they were a true 3ply sidewall. lol
Same pressure but on a flat surface. Tires move around a lot more than we usually think. :)
And then there are times when a simple little stick goes right through the sidewall of your "tough" E-load tires while on a tame dirt trail.