The XS is what I would call an Elixier with a step up in sound. I actually hadn't seen an XS 80/20 until Thomann. I looked into it on D'addario's site. It's a sensible addition to their line-up of strings. They are a little costly and wear much like Elixiers, the coating starts coming off, but a slick, easy to slide feel is there. The 80/20's have a little less tension than the phosphor bronze version and have a brighter, fuller (instead of the richer-somewhat darker phosphor bronze).