C-rated is good for larger SUV or smaller mid-sized pickups. They typically have the lowest load rating of any light-truck tire. Typically this translates to more ride comfort at the expense of load carrying capacity.
E-rated are for traditionally used for pickup trucks. Its primary purpose is for towing/hauling heavier loads. They are a much tougher tire overall, but they sacrifice ride quality as a result. Many off-roaders will use E-rated tires because they have ticker sidewalls that resist pinch flats and debeading.
SL stands for "standard load" and unlike the other two tires is NOT a light-truck tire. They are effectively tires intended for crossovers and smaller SUVS, and should be avoided if you are towing or hauling a lot of gear. Also will be lackluster while off-roading. But if your Bronco is sticking to the pavement, then SL tires may be preferred as they typically will get you the most ride comfort and the highest fuel economy.
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Personally I prefer D-rated tires, but those are relatively rare. Most of the factory Bronco tires are C-rated.
My Firestone AT2s have more load capacity than the Bronco is rated for, same with my wheels. So plenty of overhead there. The ride quality is excellent, fuel economy is excellent. They are Tyrereviews number 1 AT tire. I had them on my GX 460, which saw plenty of off-road. I never had any issues.
SLs can handle moderate off-road, gravel, wash outs, etc. I wouldn’t go through a rock garden with them, and I’d never run street pressure off-road with them.
I’d bet most people here would be better served with SLs.