While steel absolutely can fail suddenly and catastrophically, it's 50/50 (guessing, no stats to back this up) that it moves some (ie bends, deflects, whatever) and then stops.
Plastic is like that unpredictable house cat: totally fine until a split second where it claws your eye out and runs away.
If anyone doubts this just think back to prying on trim pieces or wire loom retainers -- it's always a game of will it release or will it suddenly SNAP
Given that steel is modified with relative ease but plastic is nearly impossible to reinforce or repair for structural applications, the choice is easy for me.
Again, as soon as someone starts building a reliable 2-post lift from plastic, let me know
While steel absolutely can fail suddenly and catastrophically, it's 50/50 (guessing, no stats to back this up) that it moves some (ie bends, deflects, whatever) and then stops.
I have a pair of those yellow metal ramps that are probably 25yrs old+. I rarely use ramps anymore but when I do it's usually the Rhino Ramps I grab first then these metal ones. They will be fine for your use as the full weight of the truck is not on them. If you feel better place jackstands under their for extra safety or weld some reinforcements as recommended in some posts.
I had those steel ramps and threw them away and bought the plastic ramps and use jack stands as back up. No matter what, I'm still not comfortable under a vehicle.