Which one is better, herbal tea or black tea?

 Tea is Tea. It is made from the leaves of Camellia Sinensis by carefully withering, rolling, oxidising, drying and grading. When the step of withering and oxidising is not done, it is known as Green Tea. The decoction of Tea contains zero calories and is a very rich source of antioxidants and some very complex polyphenols which is not available from any other known source of food / drink. It contains caffeine too, approx 1/7th of the quantity when compared to Coffee. All other teas like “herbal teas” are known as Tisanes. These are from herbs other than Camellia Sinensis, and usually do not contain caffeine, and of course, many of the other beneficial content of Tea.

So, in a nut shell, unless you are overtly sensitive to tiny quantity of caffeine, Tea is the drink for you. Else, select your herbal infusion depending upon your need.