I struggled with that question too. Well, my main goal was production of eggs, for sale and a few for us. Second goal was to incubate or raise a few birds for sale. So...having decided on my goals first, then I looked for the breeds that would best fill those goals.
My decision was Production Reds for my egg production goal, since they are supposed to have a better production to feed ratio than other breeds. They are, I believe, a combination of breeds that don't breed true if you try to raise them from eggs, so they fit the first requirement but not the second. So I don't want to breed these. So I bought pullets only, but will have a total of about 60 when my next order comes in the next few days.
For incubating and possibly selling chicks, I decided on Plymouth Barred Rocks. According to my hatchery's information, these are better at handling our Texas heat than many and are a good dual-purpose chicken for potential customers that just want some backyard chickens of their own. For these I included some roosters and will probably have about 25 total or so when my next order comes in.
The two types are housed together and the Barred Rock Roosters probably won't be discriminant on their choice of women, but I figure that doesn't matter since I won't incubate any of the Production Red eggs, I hope. My challenge will be identifying the PBR eggs from the Production Reds!
So for me, it was finding chicken breeds that met my goals and our climate.
Hope that helps.
Connie