In reply to s.climber:
I found Thorlo better. The smart wool and bridgedale didn't seem 'dense' enough inside the Nepal Extremes I had them in in the heel. However, other people have had different experiences.
Perhaps if it really important to you, buy one of each and do some trials in the UK, before you really use them. I didn't and fortunately only used the smart wool ones in the valley after the days on thee mountain - the spare change of socks I had carried for 4 days and hadn't used until I had a shower and was going back to the car. I had blisters in 30 minutes of walking, but had been fine with Thorlos over the mountains.
Hope this helps...