I was able to escape for a hiking trip in the Smokey's this past week and was fortunate enough to enjoy the pitch black night in the mountains. I took the U2, Gladius and the A2 to compare and I wanted to share my observations.
Night Ops Gladius:
This is a great light and it did not suffer at all from the very wet conditions. I found that the strobe function is of no value for hiking (duh). The overall output was sufficient for any task and the ultra low dimming was great for use inside of the tent. Outside of the tent, on the dark ground, the lowest setting was not of great value but the flexibility was nice regardless. I kept mine on the memory setting. I kept the light primarily on the momentary on setting as it was a complement for my headlight. This light will do anything that is required for hiking and it would be welcome in my pack anytime. I would rate the Gladius as the 2nd best in this group.
No problem with the wet conditions. The 2 brightness settings and the assurance that there will be light even after the incandescent goes dark makes this the best incandescent light I can find or have used for hiking. The overall output of the incandescent and the throw appeared greater than the Gladius and the color rendition was the best of the 3 lights that I used. I do see the benefit of using incandescent outdoors for the color rendition; unfortunately for me, I value runtime and durability over color rendition for extended hiking trips. Of the 3 lights, this would be my 3rd choice due to the volitility of the incandescent source and the lack of runtime options (both the U2 and the Gladius can operate longer at the same level of output as the A2's low beam).
Best of the bunch by a large margin in my mind. Easier and faster to switch levels than the Gladius, the low level really is low enough for most tasks and in the pitch black night, my night vision was limited to what I could see when my light shined on it. The U2 crushed the Gladius in output and I cannot see any real advantage in throw that the Gladius has over the U2 (I did notice the hot spot was brighter but not enough to make a practical difference. The output of the U2 was enough to light up entire areas whereas I had to focus on the hotspot from the Gladius. The U2 crushes the A2 for runtime (judging by the rated runtime as described by Surefire); the lowest level of the U2 is equivalent to the low of the A2 but the U2 will run for 40 hours vs. 15 for the A2. Aside from the price difference, I see no reason to choose an A2 over a U2.
Now for those that hike, you all know that the most useful and important light is the headlight. In this situation, the Petzl Zipka w/the brighter LED's worked great. I hiked for hours in the dark and used this light around camp and cannot complain. I am, however, skeptical of the lights performance in the rain. I used my Zipka in a light rain with no problem but I cannot see where it will hold up very well in a downpour (the holes in the light that the string enters and exits the light seem like an easy entry point for water).
If I could only bring one light, I would without hesitation bring the headlight and leave all others at home.