Manual microwaves are cheaper but require more work on behalf of the chef since they must manually set the time and temperature every time they use them instead of having preset options available like programmable microwaves do.  Programmable models, like this USB programmable commercial microwave oven from Robatherm, are great for those who have regular batches that they want to repeat over and over—they'll save time, so you don't have to enter every single time manually.