Since Tai Chang and Zhonghua Gate are both parts of City Wall of Ming Dynasty, i prefer Zhonghua Gate, than Tai Cheng because Zhonghua Gate is the biggest City Wall Gate in the world, and also have the exhibition of the bricks, meanwhile, from the gate you can see more views of Nanjing, more parts of City Wall. Even though the tickets is 10 Yuan higher than Tai Cheng, but if your time is a little limited, and you really want to see the City Wall, then go to Zhonghua Gate.