Tactile and climate comfort. Domestic supply chain.
Again I'm really talking about the merino line. I strive for, and most days hit, 100% wool for every layer. Before finding and buying any rambler's way, I was already satisfied by how much more comfortable merino is than cotton over the course of a day. What satisfies me about rambler's way's merino is that a) it's sheep-to-sewn here in the country I live in b) it is that bit more comfortable and durable than the competition.
To expand on the fabric for a moment, the brands I had previously found kept introducing other fibers - particularly, for example, synthetics into underwear and tshirts. I don't object to genuine advancement; however, every single blend I've tried of wool with a synthetic made the wool worse. Less comfortable, less odor resistant, and somehow despite durability being the biggest cited reason for introducing a synthetic mix, less durable. If there's any blend with synthetic I don't even try it any more.
Durability does indeed seem to be a big struggle for merino in general below a certain weight or for underwear, and my lightweight 100% merino items from patagonia and amazon all tended to disintegrate (icebreaker and wool&prince don't do lightweight 100% and even ibex whose quality I liked wasn't quite as light as yours). Your merino, however, somehow, does holds up well. Amazing.