Chengdu

A very cosmopolitan city with plenty to do and see. There are lots of foreigner commodities and a fair amount of culture. Food, from what I tasted of it, was very spicy. The weather was great and the people were friendly. The city is easy to navigate.

Chongqing

Cosmopolitan in the extreme, with people exhibiting a competitive, nouveau-riche feeling. They were not necessarily friendly. There is plenty to do and see, and plenty of foreigner commodities. For that matter, there were plenty of foreigners. Indigenous food is good. The layout is complex and, I suspect not easy to navigate in spite of the ample buses rumbling around.

Shenzhen

Nice climate and friendly people, enough foreigner commodities. Easy to navigate, but not much to see or do. Its main claim to fame is being close to Hong Kong. No indigenous food to speak of and no indigenous culture.

Nanjing

Old timey, established feel with few major commercial centers, plenty of foreigner commodities and plenty of foreigners, and easy to navigate. There is more than enough to see and do. Climate is similar to Wuhan but the air is substantially cleaner. I don't have any idea what the food might be like.

http://www.chinadaily.com.cn/opinion/2014-06/19/content_17598432.htm