An evaporator system removes the heat only while the unit is running, whereas a cold plate stores the cold and removes heat BTU’s long after the unit has stopped running. Engine-drive cold plate systems may certainly freeze down the plate faster – but you are then required to run the engine to maintain the frozen state, this may be an inconvenience or even a health hazard if you leave the boat for an extended period of time while having food in your refrigerator/freezer.