Many years ago, when we still ran fan cooled sleds, we could defrost our shields with the warm air vents. When we started riding liquid cooled sleds we had to get the electric shields. I was hesitant at first because I thought the cord would drive me nuts, but I got used to it fast. Now I wont ride without one. I don't plug mine in until it gets cold, but its great to have when I need it. My wife and I even have electric shields on our mod helmets and use them all the time. I remember a few years ago on a club ride after dinner, we were riding back to the motel after dark. We had about ten sleds in the group. A light misty drizzle started to fall and froze to everything on contact. My wife and I, and the few others that had electric shields, plugged in and where good to go. But those who didn't, (and couldn't ride with their shields open), had to stop every few miles to get the ice off. That was the longest 20 miles that I can remember.
My son has both an open face helmet with goggles, and a helmet with an electric shield for when it gets cold. He says he likes the open face better, but he definitely uses the electric shield helmet more, especially if we're riding all day and into the night.