All tea leaves are made up of the same components. Where and how they are grown and processed will change the level of each component within the tea leaf.
Tea leaves grown in shade for longer periods of time will have higher levels of chlorophyll and amino acids. This is why shade-grown teas will be brighter green in color.
Increasing the length of time of shading will also increase the level of caffeine, as well as the level of theanine. Theanine is the component in green tea that is responsible for the sweet, savory flavor. Teas that have a higher content of theanine will have a sweeter flavor, and are considered to be of higher grades.
Exposure to sunlight will increase the level of vitamin C, as well as the level of tannins. Tannins are the components in green tea (same as in wine) that is responsible for the smooth texture, as well the astringent, bitter taste. It is also one of the main components that fight cancer. Sun grown teas will generally have a more full-bodied flavor.