I think the different traditional breeds vary in terms of how they can, should and will grow, how much fat different systems will put on them, and so on.
We like Cornish Blacks (Large Blacks from Cornwall, we like to think local strains of LBs originated here but who really knows) for extensively foraging systems. If managed in a particular way, they grow slow and lean to a good size at 8-10 months. If you've forage and / or legal scraps for them, that makes sense. If you need fast growth and/or don't have anything much to augment their cereal ration, then with this breed you either rear expensive fat quickly or expensive meat less quickly. My last batch ate half a normal rare breed cereal ration, ate a lot of the waste from our microgreens operation (for which we have no other use than composting), and foraged on our fields. By 9 months the 3 of them gave a combined deadweight (gutted, on the hook) of 200kgs.
And the bacon was so delicious I literally cried.