There are thousands of words on this website. For many people it's JUST TOO MUCH, so I've tried to list what you really need to know about torches in ten short points.
1. ALL torches have two key specifications – brightness (measured in lumens) and intensity (measured in candela). The length of the beam is NOT directly related to lumens, but IS proportional to candela.
2. The distance a torch can really light things up is always less than claimed because the flashlight industry uses the misleading ANSI FL1 formula. For a "real-world" beam distance, divide the ANSI beam distance by three.
3. Ultra-high-lumen lights get very hot, very quickly, so they "step down" to avoid overheating, often in a matter of seconds. Most manufacturers advertise their run-times at peak power by adding together a lot of short bursts.
4. There is no such thing as the BEST torch – it depends on your application(s) and preferences. Finding the beam that suits you best is ultimately about understanding beam profilesand the way our eyes work.
5. However, an adjustable (zooming) beam is nearly always the WORST choice – it delivers a tiny dot of light at one end, so it's like looking through a straw, while at the other end you get a wide pool of weak light.
6. A sealed beam with a hot-spot-and-spill beam profile combines the dot of light and the pale spread into one beam, which matches the way our eyes work, is more comfortable to use, better value and more robust.
7. High-power torches today use rechargeable lithium-ion (Li-Ion) batteries. Good-quality Li-Ions are expensive but save you money in the long run. Beware of false claims on cheap Li-Ions – look at independent tests!
8. Custom battery packs trap you into buying from your torch maker, but industry-standard Li-Ions are easy to replace after 3-5 years. Note their service-life is highly dependent on the quality of your charger!
9. Nearly all decent torches, headlamps, lanterns, Li-Ions and chargers are now made in China. The very few made elsewhere are NOT necessarily better. Quite a few pretend they are made somewhere else.