Hi all, thanks for your answers.
I started this topic, trying to find a source of different links with scientific documents / researchs / studies about the words / vocabulary that we usually read on flashlight forums. Thanks a lot for some of the links already shared, because they contain really interesting information.
Personal opinions are always welcome, but really don´t help very much in my search. I don´t mind if you have a platinum + gold flashlight ,with diamond lenses, because you feel a very big improvement in the light. If you can pay it, I am happy for you (please send me another one for free, so I can test it too $) ).
I also don´t mind if people use your flashlight for professional reasons, or it is just a hobby. If you are happy using flashlights, I am also happy for you. Your reasons are not important at all.
I only want to answer the original question. Can we really see the difference?
I find very interesting some informations that have been already shared:
Tints can be different in leds with the same color temperature, tint depends on the led manufacturing process.
To achieve 2x the visible brightness, you need to quadruple the light output. 1 > 4 > 16 > 64 > 256 > 1024 > 4096 > 16384 ...
CRI is a way of measuring the quality of the color rendering, but maybe it is not the best one, as 2 leds with the same 90 CRI, can make the red color appear different, depending on the R9.
CRI is also different with the led color temperature, a 90 CRI 2700K led can show colors very different than a 90 CRI 4500K led.
I did not wanted to start to "open the pandora box" with other things than affect the light, and could be important for flashlight users, but you are right, Lightbringer, the beam quality is very affected by the optics / reflectors. This needs to be taken in consideration, and there are a lot of differences that everybody can see.
For example, I am reading the topic better low modes with dynamic PWM, I think it is very interesting. But can we really see the difference between a PWM low mode vs a Direct Drive low mode? I am not talking about a light analyser. Of course there are differences. But my eyes can see that difference really?
And also, the last comment of turkeydance, how does aging affect our vision capacity, can a child with 9 years old find differences between a 95 CRI and a 98 CRI led?
Thanks again to all that have commented. Greetings from Germany.
PS: there are many other variables, like efficiency for example. It really makes sense to reduce the battery duration to the half, only to obtain a little bit more of lumens (we already know that 2X visible brightness needs a 4X lumens quantity) and also more heat / more weight in heat dissipation, bigger batteries, etc...? But efficiency can only be measured. We cannot see efficiency with our eyes.