I just pick a yarn that looks and feels good and that’s it. I don’t really mind what it’s made of or how cheap it is.

I often knit with bargain-bin yarn, or found-in-a-thrift-store yarn, occasionally fished-out-of-a-dumpster yarn.

I have no idea what the benefits are, but clearly some people do.

I mostly prefer wool which, for me, feels a bit more lively on the needles, and (exclusive of moths) seems to survive my level clothing abuse well.

My experience is that cotton looks crisp whilst knitting, highlighting textures and stitches.

In particular, the occasional mistakes, or through-strands.

But that was not sock yarn, which may have other fibre in the blend for stretch, durability, etc.