(Red Nib Corn cobs and a small zucchini from the last few days)
Here's a short article on farmers' markets:
An article on farmer's markets compared to (American) supermarkets. It rebuts a study purporting to show the deficiencies of farmers' markets. I think the rebuttals of the study are worth skimming over - particularly the advocacy of heirloom tomatoes.
It should have said, but didnt, that species choice for your own garden is different from species choice for an industrial farm and supermarket operation. For example, the most significant value for tomatoes in supermarkets (and therefore their growers) is a thick durable skin because of travel and transport. Whereas one can eat what are not heirlooms without any problems with thin skins because there is no transport operation to worry about. Likewise, another consideration of the agriculture business is that a species is good for monoculture and reacts nicely with pesticides etc. Neither of these need to be your high priorities when selecting a tomato. (The red nib i an heirloom which you can see in the picture above - it has the characteristic of looking good but also growing better under drought conditions than yellow corn. Re nib is also extremely starchy rather than a sweet corn).
There are also underrated values that a farm does not have to think about, but you in the garden might - first, how does the plant react to rootclog in a pot? how does it react to shade and semi shade? to irregular watering? Do the tomatoes take long to go from red semi ripe to ripe? (If its a long time, thats more difficult because it lengthens a vulnerability period).
That is, to the sorts of conditions that can occur in a garden.