Water Solenoid Valve 12 DC vs 220 AC
Solenoids can be designed to work over a wide range of voltage and current.  One that works at 12 V DC is not inherently better or worse than one that runs on 220 V AC, assuming the mechanical parts are the same.

However, mixing water and high voltage is not a good idea safety-wise.  Assuming that the 12 V DC version doesn't require excessively thick wires, that would be what I'd favor.  Even better, run them from a separate completely isolated 12 V power supply.  That means any one connection to ground won't cause current to flow in unintended places.  It would take two faults for something bad to happen.