Ditto - horses for courses.
PersonallyI think Off if trying to pull away on a slippery surface where all four wheels are struggling. Once clear switch it back on & let the ECS do its thing.But regardless, its whatever worksto get you out
If you need more revs & power may be best to switch it off.
I've driven several models with 'stability programs' in snow and ice and always found it is best left on. Basically that's what it is intended for.
Whenever I turned it off I immediately tried to spin in circles. If the wheel slips then it brakes that wheel so the others with can turn and you proceed pretty much as normal. If one wheel is spinning freely then the other(s) receives no power through the differential. In fact it feels so normal it is easy to forget you are on ice and the brakes are going to be utterly ineffective: drive with great care.
Trying to switch the ESC on or off whilst the car is sliding wildly is something I prefer not to do.
Turning the ESC off on a good dry road is another matter, in fact you should try it out in safe conditions to learn what it does.
If it gets really bad then fit chains but it looks like we'll be warm and wet this winter.