I'm pretty new here as well. mpressive or anyone else, can you explain how a larger sidewall is better for offroading? How much of a difference in offroad performance is there between the SR5 stock rim/tire size vs the limited stock rim/tire size?
1) when in sand, you want to air down to increase the size of your tire patch. I normally air down my 17" tires to 15 psi on the beach. The tall side wall of a 17" tire is very flexible, and allows the tire to spread out, doubling the contact size. The 20" tires have shorter, stiffer sidewalls that do not allow it to spread out as much. Note that there are some folks who take their 5th Gen limiteds with 20" wheels out on the beach without problems, but I prefer the 17".
2) the taller sidewall provides more protection of the wheel from damage.
3) the taller, softer sidewall can deform better to adhere to rocks, trees, etc.
From a highway driving standpoint:
1) the 17" tires provide a softer ride, due to the taller sidewall.
2) The 17" tires provide better protection to the rim from potholes.
3) The 17" wheels and tires are lighter, thus giving less unsprung weight for a better ride. They also have a lower rotational inertia, probably providing slightly better acceleration, braking, economy.
4) The 17" tires softer sidewall will give the truck poorer turning performance and duller turn-in feel.
Some folks like the big-wheel styling of the 20" wheels. I don't, but whatever floats your boat.