Since in the main we need to wear helmets at work, best must be miner lamp which clip direct onto the hard hat, I don't mean the old battery on belt type, but one has to realise hard hats been to be warn, so lamp needs to work when wearing hard hat. Since cyclists also wear helmets, the lights are usually designed so you can use them with a helmet/hard hat, also designed for long use, so often a separate battery pack so lamp lighter and does not move in use.
The cycle shop one I got did have a variable output, was bright enough to light road so good work light, and battery pack not built into lamp, but still on same head band, but not cheap. The cheap PoundLand one was not as bright, and due to weight of batteries tends to slip when you sweat, but is handy when you want to take off head and use as a torch, no batteries hanging on the wires.
The miners lamp clips onto your hard hat
and the battery is on your belt, we often unclipped the lamp and lead long enough to use as torch, but clearly needs a hard hat with the loop to clip in lamp.
This
should fit head or hard hat, but it sticks out so much on the head it tends to wobble, but works good on hard hat. Note battery at back not part of lamp.
Where I worked it was a sacking offence not to have your head lamp. And they had to do an 8 hour shift without failing. That is very different to using one on the odd time your in a dark area.