Aluminum brakes steel bends
I've had the same four Aluminum rims for over 10 years. I've seen more damaged steel rims than aluminum. I will always buy aluminum unless my pocket book tells me other wise.
This only my opinion.
If you are knocking your rims against rock often, you may be running to low of a tire pressure. My trucks weights about 4300lbs fully loaded and I run at 12lbs on a 15"x8"x3.5"bs rim and 37"s. Then again you may also have a rim that is to wide for your tire.
