Of course Jerry makes a good point about spreading the heat. I however am choosing to go the ballast resistor route. I have my reasons. If I were to bet on it, I would say the resistor wire is nichrome. The same wire you see glowing in electric heaters. I worked with nichrome building furnaces for metallurgical research in my youth. I remember it being hard to work with. Terminations are a pain.

Six volt guy living in a twelve volt world