single is fine if all you want is shape retention. if you are looking for any sort of protection from dropping shit on your feet, I would strongly recommend double. Im not familiar with the 9111, but I am familiar with the 3141 chukka, which is sort of similar. The celastic is about the same, but constructed much better on the Whites. I cant remember if the Red Wing uses a man made celastic material or not, but the Whites is leather I believe.