I do Rocks and Delawares. Rocks you get to wait forever, especially in partridge - since I can't judge pencilling until they're out of juvenille feather. And rocks will develop comb faults later, rather than show them early.
Delawares is a little easier - comb faults show early, as do poor leg color. I can weed out sprigs and green legged birds early on, and know which ones to watch for poor color because they'll often start out in juvenille feather all white and never get very good.
Though side by side with my hatchery PRs, Halo's Blue and Black Rocks - made mine look like pikers... sigh. One step at a time. Halo's birds are drop dead gorgeous at birth.