Is there someone who has used both of these heads? I got GC 0.84, it is efficient but it gives me irritation and nicks if I am not careful. I read in some forums that GC 0.68 is not efficient as 0.84 so thinking to give D8 a try. I saw in a post that D8 is a bit milder but more efficient than 0.68GC. I bought GC.84sb after having really enjoyable shaves with Rockwell 6S plate 6. I found 6S 6P to be more smoother than GC.