A LOT of what they don't tell you is about this important thing LED's need call "drivers". It's what takes the battery energy and delivers it to the LED. There is a HUGE difference in drivers. Cheap lights tend to have cheap drivers. Better lights...tend....to have better drivers. Good drivers utilize the energy of the battery more effectively and efficiently, keeping the lumen output up until the battery is 'done'. Then, hopefully at a voltage that is safe for the battery' the driver suddenly and completely cuts off the light, or maybe goes into a blinking mode. Cheap drivers start out bright and simply get dimmer as the battery runs down. Yeah, they may last of hours but they get pretty pathetic toward the end.
FWIW, Big Blue manufactures very good lights (I have 2), but for the price they charge they don't use drivers of the same quality. But.....I don't know for sure about what the others use.
For a single comparison, Light and Motion (Sola lights) are very nice, really bright, quite versatile, seriously expensive, and use top notch drivers. But they cheap out on the batteries. Go figure.
If you can look at them in real life, request a viewing with batteries that are near the end of their charge. Compare that to fresh batteries. It can be an eye opener.
In real life diving it may not matter a whole lot. If you only use up 1/2 the battery on a dive, you can change it (unless it's a Sola), or charge it for the next outing. If you are doing 3-4 dives with a Sola, you are out of luck unless you run it on a low setting. Then you might as well got a cheaper light.
