If your credit card is from a US bank, nearly all of them treat this sort of transaction as a cash advance, which starts accruing interest from the day of the transaction with no grace period. You can do the math according to your own situation, but for most people it is likely to be more than just using the ATM/debit card and paying the home bank fee. Chinese banks normally do not put any additional fee on top of that for international ATM cards, and the exchange rate is likely to be as good as you'll find anywhere for any other type of currency transaction. If cc is not from a US bank, check your cc regulations for this.

On the technology side, I've seen some machines in China that initiate with a question on whether you are using an ATM/debit card OR a credit card, but not all of them do this. If you see no specific prompt on this, and you proceed with a withdrawal, and the machine refuses to process the transaction, then it's probably because it's rejecting the credit card. It is possible to get cash advances on credit cards the old-fashioned way, by going inside a bank for teller service. If you need to do this, do it on a Monday-Friday when the more skilled managerial help is likely to be around, and choose a major bank branch that is showing currency exchange boards. And allow waiting time. If Bank of China, allow lots of waiting time.

Personally, I'd use the ATM/debit card. But don't fool around with tiny amounts of money here and there--get a limit of at least $400-600 dollars from your home bank, and pull out the maximum for each transaction if you will be in China long enough to use most of the RMB you'll receive. Get a hidden money belt to wear and put the excess of daily needs there.