I like using Uni Mylar thread for spinning hair. It seems to be the stronger of the threads. I don't know what size it is because the label has disappeared. It does small to very large flies (1/0) saltwater down to a ten or twelve. The size 12 flies I have done are pretty difficult to do because of thread size but doable.
My spinning days are very few now because of the fish I now seek, but the Mylar is the strongest threads I've found.