The human eye responds to light intensity in a roughly logarithmic fashion. So, 500 lumens does not 'appear' twice as bright as 250 lumens.
I build LED driver electronics for a business and to create somewhat linear appearing steps in brightness requires roughly doubling the current per step. So, if you have 5 nicely spaced steps in visual brightness you would have e.g. 100mA, 200mA, 400mA, 800mA, 1600mA. In this example 1600mA does not look twice as bright as 800mA. More like 1600mA compared to 400mA....
This means that when comparing products, it really does NOT matter if one light is 400 lumens and another is 500 lumens (real measured lumens, not marketing b/s), you really will have a tough time being able to see any difference.
That's one of the really nice things about LEDs, they are easy to dim and you can increase runtime dramatically by just dropping down one step in brightness, in my drivers you will approximately double your runtime.
Too much light at night is counterproductive, since your iris will also get into the act as things get too bright. Then you lose night vision and burn more power in your light than you need to get the job done.
On most of my camping trips I usually just have some LED lights that are set to low level and that is plenty of light once you are use to it. Extreme runtimes and you get to see things you never would if your camp is lit up like a sports arena...
Finally, I would NEVER believe any of the Lumen figures that manufacturers claim for their products unless they provide some real proof (integrating sphere tests with certified data). Certainly Chinese/
Ebay Lumen numbers are about as trustworthy as the winning lotto numbers on chinese fortune cookies

Most of those numbers are the theoretical numbers from the LED manufacturer with 25C die temperature and top bin parts and full current regulation. Most headlamps have no regulation other than a resistor and then use pwm for dimmng, that's why they get dimmer as the batteries drain. etc etc etc...
Oh, Lumens is a measure of the total light output, so two lights with the same Lumen output could look very different depending on the reflector/collimator that is used. Focus the beam to laser-like dimensions and you can light trees 200 yards away, put a flood optic/reflector and it will barely light a tree 50 yards away but instead puts out a much more useful light pattern for a camp area. Both are still putting out the same lumens...
cheers,
george.