If you are going to diversify blood lines know what you are getting into. So as to not favor any breeder on here I will talk about another breed.
Let's say I have Buff Cochins from Tom Roebuck, one of the best breeders in the country for that Variety.
Buying from another breeder to diversify the line isnt going to make them better. I dont know that the other breeder has put in the years, record keeping, and hard culling necessary to have fantastic birds. I would rather buy again from the same breeder, one that I know is in a breed club, interested in helping youth, judging, showing to make sure the quality is there and most important....continuing to work on his birds so that the ones I buy the next time will probably even surpass the first batch. Mixing things up doesnt alway make it better, esp when you have some breeders that are dedicated, educated, informed, and concerned about doing the best they can.
There is something to be said for time spent breeding and consistency with type and egg color in the end product.