Multiway switches on 24V or 230V?
All things being equal (meaning, any wire and switches are rated for the voltage and current they will be carrying) you'll typically experience fewer losses and longer component life if the control is done at the line voltage side, instead of the lower voltage side.
Power loss due to resistance in a wire is proportional to the current squared (Ohm's law, P = I^2 * R), and raising the voltage lowers the current for the same power draw. Switching the line voltage also means less arcing on the switch contacts due to the lower current. Additionally, even though the power consumption of the power supply is low, leaving it on means using up more of its rated lifetime for no reason.
Granted, this may not make a significant difference in your specific application, but it's worth taking into consideration. If the code in Poland doesn't require one way or the other and the cost is similar for both, I would wire the switches on the line voltage side.