Thats kinda like asking what the best kind of running shoe is, everyone will say Nike because they market the best. As long as the bulb has the right K rating the light output will be the same as any other, and your plants can't tell if they are under a Nike light.
I disagree, completely. First of all, many bulbs especially the cheaper ones don't explicitly state any color temperature. Some do provide a spectral distribution graph. Of course, you realize that as an HID lamp ages it starts to lose efficiency...right?
Do you happen to know anything about how metal halide or high pressure sodium lamps work? How they are made? Not a heck of a lot like the manufacturing of sneakers. It isn't exactly as if all come from the same magical Chinese lamp fairy, are made from the same stuff or end up behaving the same.
The intense light comes from an electric arc between tungsten electrodes inside of an alumina or quartz tube; which has been filled with one or more Noble gasses (usually xenon, argon). The arc tube is pressurized and also contains mercury, and halide salts or metallic sodium. Essentially the chemistry of the arc tube determines the characteristics of the lamp including the color temperature\spectral distribution, light intensity, luminous efficiency, and even lifespan of the bulb. Aside from tungsten the lamps also contain scandium and\or other rare earth elements.
Not
all of the cheaper bulbs are 'bad'. A lot of the cheapest ones are not made with the best materials or to the best specifications. While the plants might not exactly be able to "tell", a good grower certainly could.