I run NGK plugs. The champion plugs, at least in the past, were not plated and rusted. I am not a fan of any platinum plug because I prefer to replace them at a shorter/regular interval, so the extra cost is wasted.
As for plug temperature, kief is correct. The ability of the electrode to cool determines temperature rating. A hot plug, like the BPR4EY, will tend to retain heat and prevent loading up at low speeds or prolonged idle. The problem is the plug may not cool enough to prevent preignition at higher engine speeds, effectively becoming a 'glow plug'. A colder plug will tend to not burn soot off the electrode and eventually leads to poor running. A projected tip allows running a slightly colder plug without it loading up.
If you're wondering, the code BPR means projected tip, resistor type (points ignition calls for non-resistor), 5 is stock temp. rating, E is the thread type/length, S is standard/ Y is v-groove. So factory replacement on the old trucks is BP5ES, or just B5ES.
Bosch plugs have a different code, and the heat range is reversed. A W9.. is a hot plug, a W6.. is cold.
I can't speak for ND plugs since they are Toyota specific, and I only own one gas engined Toy.
As long as the engine still runs smoothly, a colder plug won't decrease engine temperature. A hotter plug likewise won't make an engine run warmer unless you get detonation running up hills.
