What is better to use 110V or 220V?

If I had a choice I would first consider my supply. 110V is common for any house hold receptacle so I would chose 110V (if the electrical device operated at both voltages). Dual voltages like that usually mean that that they are European compatible. I believe Europe uses 220V as a common household receptacle.

Assuming a load, (motor, light, etc) is the same wattage and can take either voltage, the advantage of using a higher supply voltage will decrease the circuit amperage.

So, for example, if a 5000 watt load is connected at 110 volts, the amps will be ~45 amps, at 220 volts, (double) , the load amps will be half, or about 22.5 amps.

This will allow the circuit to be wired with smaller wire, and save on material and labor costs.