My brothers back and chest is so hairy he doesn't need anything...he has his own wool
I know the alpaca to be super soft and all the other attributes aforementioned. My other "not so hairy brother" picked up some of the same socks, I'll be waiting to hear how those work out for him.
I am using alpaca silencers on my strings and they are very durable, but that is a different kind of wear compared to compressive foot/boot contact.
As for myself, I have a lot of Merino wool and in particular, Smart Wool, love it and couldn't have enough of it.
Love natural materials, all are better and healthier than a lot of other things (polypro) and better and more sustainable for our world.
We're likely splitting hairs here between different wools...pun intended.
Kris