This is Toyota specific but think of it as very helpful in general, on what we should want for skid plates. My conclusion is 1/8" steel at something less than 2x the price of 3/16" aluminum.
With the front bumper skids that are out. Either the aluminum or steel will do fine. Not going fast enough to do much to either. I’d do steel under because you’re more apt to put a lot more weight on it. Plus the front bumper skid mounting point isn’t very robust. I’ve put the weight on the oem steel engine one and held up well.