Did you get both groups of birds from the same source? Sometimes it depends on the focus of the breeder or hatchery whether their birds will be exceptional layers, no matter the breed. If one doesn't breed for it or cull for it within their breeding flock, there likely won't be as many great layers in the flock. Some hatcheries focus more on laying with their production breeds but not as much in the individual dual purpose breeds...those they will just breed for the breed, most likely.