What you need to look at is the power output or the wattage of the ovens. if they are bothe the same then THERE WILL NOT BE A SIGNIFICANT DIFFERANCE IN THE TIME IT TAKES TO HEAT A CHAMBER OF EQUAL SIZE. If the 220v oven with the large chamber has the same watt/power as the smaller chamber 120 volt oven then the 220 volt oven will heat SLOWER than the 120 volt oven. On the other hand if the 220 volt oven has a higher wattage heat coil in it it will heat faster. How fast depends on the wattage.
ABS Master Smith, 2008