OK.. I guess there is no right or wrong answer for this question, so let me start this with a story.
"Many years ago, there was a poor guy in a remote Chinese Village and he owned a clay teapot and the teapot had been using for generations. One day a city man came to the village and saw the teapot and he was very impressed by the teapot, so he decided to buy the teapot and paid thousands for it. He told the village guy that he would pick it up next day. The village was so excited and he reckoned he needed to give the pot a big clean, so the buyer would be happy about it.
Next day, the city man came back and saw the teapot was very clean, it was so clean that there was not stain at all. The city man then was very disappointed and decided to drop the sale. The village man didn't know what went wrong and just found out that the teapot wasn't worth anything, but the tea stain that got built up by generations was worth the most."
This story tells us that Chinese have a long history of using clay pots and the clay pots themselves enhance the tea favour because the "stain" adds favour to tea. Also, temperature can be controled better with clay pot.
REMEMBER the mort IMPORTANT THING ABOUT TEA!!! You are not supposed to leave tea in the teapot for more than couple of mins as the acids from tea would come out if you leave the tea in pot for too long.
What I wanna say is advantage of using clay pot will enhance tea favour, but it's a very personal choice. Glass pot is fine and just don't leav tea in the pot for too long.
Also, avoid using metal pots as the chemical reactions between tea and metal don't go too well..