On the basis of research so far, some teas stand out in certain respects. Here is a tentative summary of the claims made based on research to date:

Digestion                             All kinds
Anti-bacterial                   All kinds, but not fully confirmed
Cancer prevention          Green
Heart                             Oolong and Pu-erh for cholesterol, 
                                      green and oolong for blood vessels
Slimming                        Oolong and Pu-erh
Tooth                              careGreen
Longevity/Anti-aging             All of the above; special 
                                             emphasis on green for fluoride 
                                             to combat osteoporeosis

Whatever modern science finally concludes, the intuition and experience of ordinary people has certainly built tea a reputation as a healthgiver over the centuries.

- As described in the book, All the Tea in China
  by Kit Chow & Ione Kramer (1990)