THis implies, if I am understanding this fully, that folks looking for a good start in a heritage breed would greatly benefit from finding a local breeder where the poultry has already adapted to the local conditions; or be willing to deal with possilbly a poorer performance during the time of acclimation. I would think the latter would be a difficult obstacle to overcome for anyone new to breeding high quality birds.
When I was growing up in Maine, only brown eggs were at the grocery. ANd to this day, white eggs look strange to me. THis reflected the type of bird that thrived in the Maine climate even when kept in a commercial building. Or perhaps when commercial buildings became the norm, brown eggers were used because that what the product the consumers were already accustomed to.
Another variabilty I am seeing between breeds is matureity-- I expect this reflected the local diet and management style in the development of the breed. Perhaps a breed that took longer to develop also required less feed day to day whereas others that are fast growing and maturing reflected an abundance of readily available foods.
ANd what about disease resistence-- I would expect local issue that might be common in one area to be not a problem in another. SO again buying poultry already adapted to the local area could be a bonus for those somewhat new to poultry.
I would not let local limit me. I would take these things in consideration when I decided on my own personal ideal. Then I would go for it, searching far and wide to find the best that I could come up with.
If you were fortunate enough to find a REPUTABLE breeder in your area with birds that you would be happy with, then that would be a great way to start. I had to search from coast to coast and border to border to find what I wanted. With our new ability to access and exchange information, there is no reason to settle.