OK,
found it. Skip the sections that are really interesting anthropological theory, you can tell within the first paragraph of a section whether it is theory stuff or literal description of the giraffeing/selling/cutting process. The first section you want is "The Political Economy of Bluefin Tuna," skip Scapes and Chains, skip Multi-Sited Ethnography of Things.
I think he basically ends up saying that there
is a difference, but that most people probably can't tell the difference. I also read somewhere that thinking home-raised eggs are tastier is all in your head, and people can't tell the difference in a blind taste test. That said, I think eating food that you or your friend raised is a good cultural/social experience, and can make your meal feel more meaningful or enjoyable.
I think about this a lot with coffee, because I used to think people who claimed to be able to distinguish tiny differences in coffee were just jerks. Now I am pretty amazed at how different coffees made in different ways, with different beans, etc can taste. That said, I don't have a strong preference for any particular kind. I add plenty of milk and sugar anyway. What's really amazing is espresso-- adding 1/4 gram more grounds, or grinding them one little notch finer, or running the water for a second more has a huge effect on the taste. I guess it makes sense if you think about it as really tiny, high-pressure high-temperature cooking. Getting the flavors in balance is hard.