I agree with Jeffy. I have nerfs on my jeep and have beat them to hell. They do the job. haha. For the price I dont care how much I beat em up.
Mine are the old shorty's. They're huge. If you're rockcrawling on some large rocks then they can be a problem. If you're not then it makes little difference. Although i bought mine back in '93 when they were still vogue. The new slider nerfs are much smaller 1-2" instead of 3". You can also have them wider so they're 4". Really nerfs are sacrificial though. Before the slim craze started people were making them from scratch for cheap.
One thing to consider about the rocker skid plates is that it leaves your body mounts exposed and you'll hang up on those as much as you would on a nerf. It is also important that the rocker skid have straps on the inside that the bolts pass through. Not everyone does this and it is important. Sandwiching the body between two plates makes for a stronger mount. The nice thing about angle iron is the edge is thicker then if you used bent steel/aluminum. I'd still probably weld a rib kinda like what Art did. This will help keep the panel straight when hit. Also, if you make them yourself you can run them the full length of the rocker. Most stop short on both ends to account for the flares.