I should think that most of them are worth butchering. I don't know much about the differences between the different breeds, but know that silkies are supposed to have dark-colored bones & meat. I have lots of mixed-breed bantams & have reached my limit of pretty little pet roos to keep. I'm not going to set any more bantam eggs for a while just so I don't have little roosters to deal with.
But I butchered a bantam last time I did a few other big birds, he weighed a pound after skinning & cleaning. He was easy to handle, skin & clean out and made a nice break between all the other big roosters. They were all about 20 weeks old & as meaty as they were going to get. I quartered them all & simmered them very slowly in herbed water for a few hours, then pulled the meat for use in other dishes. Everyone was tender & tasty.
I do have an extremely tiny Dutch bantam pair someone gave to me that we're going to keep around. I don't think he will cause problems with the other roos, and really is too small to make it worth the effort to process. As long as he continues to behave himself he can stay out of the soup pot.