Which Ancient Water town is more authentic and better to visit?

I have browsed through the message board and ended up with the following water towns:
Xitang, Qibao, Zhouzhuang, Tongli, Suzhou, Wuxi.
I am bit confused on which one or two to choose to see in one day. We will be staying in Shanghai (Pudong district) in January and I am thinking of a day trip to the ancient water towns. Which ones would you suggest visiting?