Green tea is better for than black tea. White tea is the best. They are all the same plant/leaves, the difference is in how they are processed. Black tea is green tea which has been oxidized, that is why it turned black. When you buy a green tea, the greener the leaves, the fresher it is, and better it is. Whole leaves are better than "dust." White tea is the young shoots of the tea plant, they have the most antioxidants and almost no caffeine (very little taste, either). Pu-erh is also the same tea leaves, but they have been fermented. This is what the health properties of pu-erh are attributed to. The older it is, the more valuable. A decent one might be 10 years old. A luxurious one might be 200+ years old (you might collect that instead of drinking it).