I did not have many chances in different cities, from my experiences in Beijing, Shenzhen, Yiwu and Shanghai, I shall name Shanghai at the 1st place. 

I also agree on Shanghai. I have lived in Bejing, Shanghai, and Guangzhou, as well as several other cities. In my experience Shanghai was by far the most convenient. Second place would be an even tie between Beijing and Guangzhou. And in third place I would rank Shenzhen (only because I lack more experience living there). They're all great cities!

Shanghai without a doubt.  Getting better every day (I mean the public transport) and worse every day (I mean the cars, trucks, buses, etc.)