What's the difference between hatchery or standard bred stock?
Standard bred stock is bred to the American Poultry Association's (APA) Standard of Perfection (SOP) . This means that the birds have a specific standard that they are supposed to live up to which includes things like weight, type (type of body such as round, brick shape, etc), particular details of color, pattern, comb, feather width. Standard bred birds take longer to mature and thus can get quite large.
Standard bred birds are not "egg laying machines" like most hatchery birds. While egg laying can usually be improved in an SOP flock, they still don't usually start laying as early or lay as often as a hatchery birds. Which means that their years of productive egg laying can be upwards of 4-7 years while most hatchery hens fizzle after just a couple of years of laying. Standard bred birds are also more prone to go broody.
It takes a lot of work to breed to the SOP because you have to look at the birds, see what their faults are, see what their good points are, and then make breeding decisions to try to improve on the flock by offsetting one bird's faults with the good points of another bird. And with being slow to mature, you may have to wait until they are a year old or more until you can decide which one is the best to breed.
Hatchery stock generally gets bred indiscriminately, except for high egg production. Hatcheries can't make money by being picky with breeding. They need as many chickens breeding and laying eggs in order to make money by using the QUANTITY of eggs/birds sold as their business model. This type of breeding may mean that there may be large variations in the offspring's temperament, as well as physical characteristics. They are also usually smaller birds, faster maturing.
Most people see color in chickens but there is a lot more with shape, stance, other physical characteristics that actually make up a bird. These specific characteristics often (usually) start getting lost in hatchery stock. If you were to see birds in black and white photos, you may not be able to tell what breed a hatchery stock is because their physical characteristics aren't as obvious as a well-bred chicken.
There is a place for both kinds of birds. It depends on your goals with your flock as well as the time/money that you have available/willing to spend as to whether you might be better off with hatchery vs standard bred.