The following will be pretty familiar to many here but for those moving into the world of LEDs (welcome) or wondering if spending more gets you more I have a couple thoughts that I think are worth while.
Color: (or rather color temperature) During LED manufacturing they are sorted based on the desired specification (search product binning) Cheaper ones are allowed a wider specification. One of the hard things to do with LEDs is to get good clean warm white, or true white which is why many small lights seem to cost quite a lot. A lot of cheaper LEDs or LEDs that have been over-driven to get more output get a purple tint to them. This is partly just annoying at first, but if you need to do any close tasks with them, the color can lead to eye fatigue pretty rapidly for a lot of people. Odd colors can also make tasks like map reading, or even walking in the woods very difficult. I've come across a few that had a green or blue tint, and those were very bad against trees as the contrast made it very hard to focus.
Dimming: LEDs cannot be dimmed quite the same as an incandescent. What normally happens is the LEDs are turned on and off rapidly. This is sometimes done to extend run-time, is often adjustable on lights that have more than one feature. Its good if you need to do close work, as the light pattern of LEDs is more glare inducing than incandescent, so less becomes more. But that flicker can often be seen by others around you, even if its just indirectly. They become a bug magnet, and a cheap PWM (pulse width modulation) light in rain is very hard on some people's heads, and long close work will be very tireing. More expensive lights use higher rates of modulation to get the same effect, and there are other methods always being developed.
Vampire drain: better lights tend to not drain batteries when not in use, but its not always the case. For a very long time Princton Tech was notorious for it, and even some of my black diamond lights need a refresh every six months or so.
Pattern: Cheap lights tend to just blast a big blurry haze of light from the LEDs. Because of the way light comes out of an LED chip it takes some real work to make lenses and reflectors for them, and that has a cost. A lot of times it is not as noticeable, but in any sort of dust, smoke or even light fog, you might as well be shining the light in your own eyes, and the only remedy is to hold the light out in front of you like you would a hand-held.
Runtime: The FL1 standard which some makers use is the time it takes for the light to be outputting 10% of the initial. Some makers list based on best case situations where you can still cast illumination a very short distance. The drain curve on LEDs and alkies means some lights will run for days where there is still light, if you look for it. Obviously not everyone follows it, even some of the high-end, but it gives you an idea of what they really mean. Some lights are long useless before they get to 10%, depending on your needs.
All this adds up to, being around a bunch of kids with cheap LED headlamps is very annoying. You probably don't want them to have features like strobes, and you might want to spend an extra couple dollars for battery doors that are attached. One of the first things I teach the kids I'm working with is that its not a headband, its a neck strap. This keeps them from shining you in the eyes when they talk to you. All in all if a dollar light is all you are looking for, then by all means, go for it. But if you are looking at survival equipment and thinking that all lights are created equal, then it could be a rude awakening when that light doesn't work well with your vision.
Obviously the last few years the tech has really taken over, and the cheap end of the market is really getting flooded. But the saying "you get what you pay for" rings just as true as it ever did.
