How to find and compare two regulators' output impedances
Both devices specify parameters called: -


Load regulation (how much the output may change under load)
Output resistance at 1 kHz (related to the above)


Neither device specifies the AC output impedance because it will be always assumed that the parallel output load capacitance will dictate that i.e. 10 uF at (say) 100 kHz has an effective AC impedance of 0.16 ohms.