Pros: Docile, beautiful, very large
Cons: slower growth and slightly poorer egg production
We had Black Jersey Giants. One became our flock rooster for a couple of years. He was huge and beautiful, with solid black eyes, iridescent plumage, and a very upright "proper" stance. We could pick him up and carry him around, and he wouldn't fuss, yet we have had him jump on a hawk that had one of his hens pinned down. Harvey was our favorite chicken ever, and was only let go because so many in the flock were his offspring. Harvey moved to a nearby farm where he is still going strong, despite being 5 years old!
Very large birds that grow a bit more slowly than the other heavy fowl. Extremely docile. Hens did go broody for us some, and laid reasonably well year round. Eggs were usually large and x-lrge. They were quiet birds for the most part, and not aggressive with other members in the flock. Easy to make these into pets. They faired well in free range life, foraging well and not being plagued with any health issues. Seemed undisturbed by heat and cold. The docile temperament is evident even in crossbred offspring.
Crossbred chicks from Jersey Giant crosses have grown very fast and reached processing weights much faster than did the purebred. Carcass of the purebred is acceptable, and they picked surprisingly clean for a black-feathered breed.
A good homestead bird, but not a steadfast producer like the plymouth rock or rhode island red.