It always depends upon what you are cooking and the quantity of it.  If you are doing the veggies for a bunch of people, then, of course, the electric device will save a lot of time so that you can do something else.  However, if you are just chopping one or two, then it doesn’t matter. Sometimes you will spend more time using a machine, as you will need to clean the blades, the container and then dry them thoroughly for the next use.  If you are doing some hummus, a knife will not be enough for you. You will need something more substantial to mash the chickpeas perfectly, which is simply a chopper or a blender.