It could be it is for less heat;, more/less light;, if they ran at 18v constant which is normal for command;, or if they were just all that was available that day.
The life expectancy and lumens could be closer.
Rule of thumb a 12v bulb burns half as bright for twice as long on 6v. Twice as bright for half as long on 24v. Actual heat build up at unexpected voltage varies on occasion though, and some originally used bulbs are too hot imo. I always bought small bulk to have had a decent variety to test with until even Radio Shack closed leaving no more local electronics shops around that I know of. I 'll be settling for the autoparts store choices more often than not.
