I've had a few now and there seems to be only minor differences between the Single casks I've had. It really depends what you want from the Connemara? The cask strength always seems to have more peat in it to me where as the Single casks are surprisingly more refined. Probably has something to do with the ABV difference but both are far superior than the NAS and better value than the 12yo IMO of course.
I am really looking forward to opening the Connemara Sherry Single Cask very soon