this link:
http://www.ledtronics.com/ds/aut1157/
sells LED tail bulbs that output 100lumens in red...
this link:
http://findarticles.com/p/articles/mi_m3012/is_2_184/ai_113602893
On top of that a typical rear stop function an incandescent bulb needs to generate about 400 Lumens of energy to net 75 lumens of energy by the time it gets through the red lens. A red LED only needs to generate 75 lumens because you don't need the red lens.
not saying anyone is wrong, just trying to get clarification...
when someone says it won't perform as well/efficient... HOW much difference? 10%? 75%?