I don't think it matter much how you turn the slinger/spinner whether it be electric, ground driven or pto. What is more important is control of the material flow because you can stop and start the spinning easily enough but the fertilizer will continue to drop through until you close the gate/chute. If they had an electric solenoid operated chute control that you could index I wouldn't care if the spinner turned continuously. This is my pet peev with spin spreaders in general, you need remote controls for the gate/chute.
One good thing about all mounted spreaders is they are more stabil than the small pull types. I have had my pull type tip over in quick turns, that wouldn't be a problem with the mounted electric units. Using an electric motor to turn the spinner shouldn't be a problem as far as I can see.
I am going to fertilize my lawn tomorrow and think I will try using my larger spin spreader on my x749. It should throw a much wider pattern and the weight isn't a problem with only 120 lbs of fertilizer in it.