if nothing else, shorty headers are quite a bit lighter than the stockers. If you get 10 hp from the headers and lose 20 pounds off the nose of the car you win. Especially if you aren't dragging over every driveway and speed bump.
The evidence shows that shorty headers are an improvement over stockers on a dyno. For the same cost and less gains, many people happily throw on over-sized throttle bodies and plenums. And they don't benefit from any weight savings. Installation may be a hassle, but it's a one-time thing.
Long tubes are better for power, I don't think anyone argues the point. But they cost significantly more, especially considering the fact that you need to replace at least the mid-pipe as well. And anyone who needs to pass California-like emissions has few other choices, regardless of opinions. And it's not like nobody lives in California :/