FWIW - I pretty well destroyed both the OEM steel skid and a TRD Pro (aluminum) one. I think the steel one gets dented up much easier, but is stronger and I would trust it to handle repeated abuse longer than the aluminum one. I collapsed the middle of the aluminum one on my first difficult offroad trip. It did not fail completely to the point that anything protected was damaged. However, it was no longer structurally sound. The steel one looked like a raisin after a few years, but was still more structurally sound than the aluminum one after one difficult trail (the Rubicon in California).
I ended up building a custom steel version of the aluminum plate. But I probably have a few tools you don't.

It held up very well, but the weak point becomes the rear two mounting brackets. They will eventually collapse if you play too hard on the OEM mount points only. That's why the aftermarket ones extend back to the next crossmember - it provides a much better structural point to mount to.
If you want to go play in the rocks regularly - you don't really want either. If you want to use them for the occasional impact on rocks - both are probably similar in terms of protection. They will both protect everythign above them from all normal gravel and rocks from other vehicles and from pretty decent impacts on other stuff. Neither are intended for regular rock crawling. If you want to do that - buy an aftermarket set of skids. By the time you're doing that you'll also need sliders, gas tank skid, and lower control arms at a minimum IMO. That's why they tend to all go as a package.
I like the look of the aluminum one better. So, there's that.
Good luck with whatever you choose. They'll all get you home. The aftermarket will just last longer to repeated abuse.