A little over a week ago, my Switchback 3 died right before my commute home, almost leaving me stranded. After I sent it back under warranty, I decided that I wasn't going to be in a position of having to rely on just one light at any time, so I ordered a pair of Fenix L2D Premium 100 lights. I received a new SB3 via mail two days ago, and received the Fenixes the day before that, so tonight, I took them all out for a ride, along with my cruddy Blackburn Quadrant. I tried to use my digital camera to take videos of beamshots, but none of them came out. Anyway, here is what I found:
First of all, the Fenix lights are BRIGHT! On turbo mode, the two lights had a very intense spot, and if necessary, one could ride at a decent pace with just one L2D. With two lights, properly aimed, you can get nearly the same coverage as a three LED PT Switchback, and a more intense spot. The big drawback is the lack of spill to the sides using the Fenixes. You really need two lights to get good coverage. One light is a little too spotty on its own. You'll have a white spot in front of the bike, surrounded by dark. Two lights give you a good fill. I purchased two lockblocks to attach the flashlights to my road bars. They really don't work very well. They don't give you much flexibility in aiming the lights, even minor changes in aiming the lights tend to reset themselves with the next pothole.
Initially, I thought the L2Ds were significantly brighter than the Switchback, but as the ride went on, I noticed that the Switchback worked much better at floodlight and spill than the flashlights did. Whereas the Fenixes has a very intense small spot, a larger well lit area, surrounded by blackness, the SB3 had a fairly mild spot, and a very large flood area. While minor changes in the aiming of the SB3 did not have a drastic effect on viewing the road, improperly aiming the Fenix did.
Overall, though, I was very impressed with the Fenix lights. For less than $100, you can get a light, four AA batteries and a charger, and will have something that can outshine most lights in its price range, and a few that are significantly more expensive.