I’ll copy-paste what I put in that previous thread.

You want real, non-stretch jeans or canvas. Bonus if they tell you the weight of the fabric. Once you get any spandex in there, you are limited in strength. I also always go for pants with reinforced crotches, cause otherwise that fails first for me.

In order for pants to stretch, the cotton (or whatever other blend of fibers) is essentially held together by spandex fibers. You might get the feel of the cotton, but the structural integrity of the garment is dependent on the spandex. Spandex wears out, especially if washed and dried a lot. In some cases, this results in the pants just getting permanently stretched out, but in other cases the fibers just come apart in a way that you can’t really repair.

I really like pants with a crotch gusset, because that’s where mine typically wear out. That gusset prevents the wear out, but it is also easier to repair if necessary. I have a pair of pants with a spandex blend gusset, and plain cotton throughout the rest of the pants, and ibthink that’s a good combo of durability, repairability, and mobility.