More durable than SW!
Check out this blog post: http://travellingtwo.com/resources/merinowoolsocks-icebreaker
According to the bloggers: "The Icebreaker socks (on the left) have been used intensely for over a year but dont show a fraction of the wear that the much younger Smartwool socks do. The Smartwool socks in this picture saw irregular use over 6 months. For this reason, Icebreaker is now our favourite brand."