Electric heaters all put out the same amount of heat. They are all ~1500 watts so the only difference is how they distribute the heat.
I go for the smallest cheapest ones ($15.00 to $25.00) available it will do just as good a job as one 14X the cost.
Dick
2002 43' DP Beaver Marquis Emerald Cat C-12 505 HP, 1600 Tq
2003 Jeep Grand Cherokee Overland ---toad