Besides being larger and can carry heavier loads and armour, the advantage of Ka-52 is that it has 2 radars, one on the mast and the other inside the nose, capable of tracking and targeting aerial and ground targets.
Standard Z10 has no radar, though a new mast radar has been developed but we have not seen them in services yet. Rumour on China buying Ka-52 thus has some weights in it, Ka-52 can also be used as a bench mark reference for China's development of heavy attack helicopter.
The downside of buying Ka-52 is the uncertainty of delivery due to Russia's production commitment to their war in Ukraine.