Ideally, you need to be able to feather the valve to get the adjustment just right, sometimes a gradual adjustment transition. electric valves are either open all the way or closed. Yes you can flick the electric control switch off-on-off-on, but what you actually get are little jumps in the adjustment, not a smooth continuous transition.
They obviously work, or they would stop selling them.
But as I said, not the ideal controls for something that often needs a fine gradual adjustment.
They are definitely better than manual adjustments, but that's about it IMO.