As Don said, I believe the oil filled are the safest, especially if you have kids or pets around. I got this little 400 watt oil filled to use as a supplement.
oil filledWe use it to avoid winterizing in borderline twmps. In my 27' Winnie it will keep the temps about 12 degrees warmer than outside on its own and then we set the furnace to 40-45 so if it gets too cold the furnace still kicks in.
And at 400 watts it's not hard on the 30 amp load limit we have in our rig.