The range of climates, micro-climates, technological level, cultivar availability, weather patterns, land use patterns, farming/gardening practices - to name a few - of urban areas, considered globally, make it impossible to determine useful comparative statistics.

In general, horticultural techniques yield more food value per land area and diverse agricultural production operations (many different crops and mixed-use areas) yield the highest food value.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre