I own a set of platic ramps... . my 2500 4x4 collapsed my metal ones.
That was some funny feeling, know I should be driving UP... a ramp... and instead getting this sinking feeling as I drove "UP" the ramps. I'm glad it happen how it did.
The plastic ones that I bought from my local shop are engineered really well. Every square inch (literally) is supported. There's a very heavy boxed web support struction that transmits the load from the ramp surface to the ground.
Solid sides, unlike the metal ones that can spread.
After owning these for the last two years, I wouldn't buy another set of metal ramps again.
Bob