Personally I think you have more control over the entire process with all electric. Two reasons are tops in my mind. First is mash temperature control, I believe this is superior in a properly designed electric system.
Second is being able to repeatedly control boil intensity via a know power input versus a burner sound or flame appearance. This allows me to make small changes in the boil off batch to batch if necessary to correct any small efficiency issues in the mash. I can vary boil off from 1.1 GPH to 1.6 GPH simply by changing the boil power, this is priceless to me.