I have a 2019 4Runner which is lifted, beadlocks and has steel skids. I beat the hell out of it (broke my steering rack twice, broke my rear axle shock mount, broke a control arm... and so on). Point is to say I beat on it. It's currently getting the RCLT kit installed. I have steel skids on it and have yet to seriously dent or bend them.
I just purchased a 2021 4Runner for my wife. It's being built as a light overlander as we have 2 kids and don't all fit in one vehicle with gear. She will be going on trips with me that are more overlanding (not hard trails). So I decided to get RCI aluminum skids to save weight and make it a better commuter. I can tell you that they are much lighter than my steel.
This past weekend my friends decided to go to Coyote Flats. My Toyota is in the shop and I didn't start on my wife's yet. On Thursday I threw on the aluminum skids and rock rails that I had waiting for install and took my wife's 4Runner on the trail with stock suspension and tires.
If you haven't been to Coyote Flats (to Funnel lake and the campgrounds around Baker Creek)... it's not a difficult trail. On 33's with a lift anyone can make it. If your stock... your fine too but you will get some rock rash underneath. I honestly was easy on the rig, took my time (which is rare for me), and made sure to be as light as possible using the skids... but I used them as they are intended to be used.
Came back home with cracked welds and a bunch of dents in the skids. They did their job but probably won't be able to handle another trail without repairs. RCI did a fantastic job with the skids... not their fault at all. It's my fault.
I always used steel skids. However, after reading a ton of comments on the forums I got convinced that aluminum was good enough for this build. Now I know that aluminum is only good enough for a pavement princess that goes out on easy dirt trails with small ruts once in a while. Definitely don't let your aluminum touch a rock.
Just figured I'd share a real world review...