Neither. Take some USD/EUR/HKD (whichever is easier) with you and get them changed locally if the ATM doesn't work.

Situation with ATMs during my recent visit to CAN (and Panyu which is a smaller Guangdong city): Cirrus/Maestro does not appear to be very common and VISA, while theoretically accepted by most ATMs, doesn't work everytime. Moreover, outside of hotels/restaurants catering to foreigners, don't expect to be able to use (non-Union Pay) plastic to pay for goods/services.