On our side, China Merchants Bank has the best exchange rate, low handling fee, followed by Industrial and Commercial Bank of China, and China Bank is the most expensive, probably because people think of China Bank first to exchange foreign exchange, and his family has no worries about business.
Of course, it may vary from place to place.
In fact, if you do online banking, the exchange rate is easy to find, and some banks can see it on the website without online banking.