[DutchmenSport]

From a logistical standpoint, I think the skirting would be easier. In order to install new tank heaters where none currently exist, you'll have to run power to them. Tank heaters run off your camper battery (DC). So, somehow, you'll need to run wiring for power. I think that would be a bigger challenge than putting up skirting.

If you are located in Vermont, then there isn't enough you can do to brace yourself for winter. If at all possible, do both .... the skirt and the heaters (and the extra insulation).