I prefer to Buy food from someone I know feeds the same food to his family. While I cannot control his growing methods, I believe that the farmers I have met and spoken to would not knowingly follow farming practices that would harm their families.
I have also found that the flavors are richer and more diverse.
(my family now refers to grocery store tomatoes as 'Red Styrofoam')
I also believe that the short travel time leaves more of the nutrients in the produce.