a wax iron is the way to go, buy the cheapest one you can find. mine cost 15 bucks and it has been working for the past 5 season, but it is time to upgrade as my heating element is starting to go a little crazy.
the reason a wax iron is better is because of the temperature control so you can use the recommended temperature on the wax. granted it isnt that hard to find the right temp on one w/o a dial. Also the heating element is thicker and its range of heat is less, so say you set it for 75 it will go to 70-80 on that setting, where a clothing iron has a much broader range. like 60-90. since it wasnt meant to sustain a constant temperature.
that is also when you get into higher end wax irons (dont do it, waste of money) is that they have a thicker and better heating element. so that way when melting waxes it stays more constant. this is pretty important when you start getting into melting flouros as they are a much harder wax and require a lot of consistency in the temperature, meaning that they smoke very easily. SO that is why race teams will have a fancy digital thermostat iron.