The thing to remember is that watts are what heats the chamber not volts. It doesn't matter what voltage you use to get to the wattage that you are using to heat the chamber 2200 watts will heat a 2 cubic foot chamber in y amount of time and it doesn't matter whether you are using 20 amps at 110 volts or 10 amps at 220 volts. the only way that 220/240 volts will heat this same size of chamber any faster is by increasing the wattage through increasing the amperage. if you use the same heating element for 220 volts that you used for the 110 volt then you will double the wattage of the oven and decrease the heating time though not by half.
The biggest reason to use 220 volts in making an oven imo. is that for a given wattage you will draw half the amperage through your shop wiring ie.. 10 amps @ 220 volts vs. 20 amps @ 110 volts this creates less heat and stress on the wiring and service panel in your shop.
ABS Master Smith, 2008