The rare breeds are different in every conceivable way,
commercial pigs are just that, they do not experience compansionship from others of their breed,
they are artificially inseminated, whether they want it or not, this is not life but hell for an animal whose social life is
it's basic pig instinct.
I think it all depends on the particular farmer's relationship with the pig,
Our rare breeds, enjoy life to the full, we cater for all of their needs and in return after a reasonably long life
they give us good food in return.
The less trauma to the pig the better the taste at the end of the day.
I could go on, but I won't.