Overall, it is hard to beat a good Silkie. They will be the most broody and generally the best mother.
However, just as with people, some are good at something while others aren't. It will always depend upon the individual bird.
But your chances are much greater with a Silkie.
You can often get a good brooding hen from a Silkie breeder. They usually have a 2 or 3 year old girl that is a proven mother but do not need anymore. There are only so many brooding hens you can keep, and if this girl is imperfect in coloring or overall appearance (but in good health...just not show standard), you can get a good deal as well.
I have found 2 faithful mothers that way.
My next choice is bantam Cochin. I went to a farm and purchased from a line that the owner was using to hatch turkey eggs. (Yes, turkey eggs.) These 2 girls were pullets from a very, very broody mother. Both proved to be good mothers.
LofMc