this thread is worthless without a link.
And, sigh, I love how the actual materials science and engineering takes a back seat to the 'marketing' with the big crane standing the crane on edge. Aluminum and steel are both different materials with different properties. These materials can be manipulated in certain ways to gain the desired results. Varying the composition and grade of the material, (steel alone is an alloy that has hundreds if not thousands of different recipes), and physical attributes (thickness) as well as the shape the material is in (ribbed, folded, corrugated) will determine how well a material holds up to a given task.
I hate this whole "we use aluminum now and aluminum is superior to steel" tone of this video commercial. Any material can be engineered to be impact resistant, or light, or both. I'm not saying Steel is superior to Aluminum, nor am I saying the opposite. The only reason the aluminum 'seemed' to fare better in these tests is because as a whole, the bed of the truck deflected more therefore the immediate area dented less. The steel bed as a whole resisted the impact better, but the immediate area took more damage.
BTW, Aluminum is significantly less ductile then steel and will fatigue more and break easier. This is why they don't make the truck frames out of aluminum. Again, not saying aluminum is inferior, just different.