tkl,
That was my comment. My SL-20 was purchased in 1978. All heavy-duty aluminum with a sturdy, near-indestructible switch. The switch did have to be replaced after I left the light on my hood a minute, then took off after a drunk who almost ran over me. I remembered the flashlight on the hood just as it departed, at 60+ mph. After I snagged the drunk, I went back a few hours later and found my SL-20 in the ditch. The switch body was all busted up, but it still worked. 'Nuff said.
The newer ones, in the past ten years or so, have a different switch that isn't as sturdy. I gather that from the number of complaints I've heard from other troopers, and these guys USE the lights regularly. The complaints range from short lives on the bulb/reflector assemblies, to the switch puking. I bought five spare bulb/reflector assemblies with the light, and the only time I've had to replace one is when the light suffers major impact with the bulb illuminated. I still have two left.
Then, in a recent thread here, I read where the light output of the current issue isn't rated as high as what I have. The information there was a bit confusing to me, and I never did sort it out for certain. But I am convinced that the current production SL-20 isn't as sturdy and durable as my 24-year-old version.
I think the Ultra Stinger has rendered the SL-20 moot; unless you feel you need the size and mass of the SL-20. If I had to replace mine, I would get either the US or a TigerLight.
Steve