Yes, at that distance, on that size of display, the difference should be very easy to see.  But, most people do not sit 5 feet away from a 65 inch display.

I used to think that. And it was probably true 10 years ago. But, the reality is that many modern LCD televisions are great.  

It is unfortunate that plasma didn't work out in the market long-term. It has a lot of benefits over LCD.  In many respects, the change from plasma to LCD set television performance back a decade or so.  But, the industry has moved past that. A new, mid-level LCD television performs better than very good plasma TVs did near the end of their time on the market.

Of course there is, the luminosity is the main focus for me and trumps all else. Having three different light scoures or more crossing each other in Metro Exodus and one seemingly blinding you yet still being able to see the environment as if through the light rays in Metro Exodus Is crazy cool. I don't know much about colour blindness but surely having bmmore natural lighting scoures with a wider range from black to full luminosity would have to be a boon for the colour blind more than anyone else, No?

It was already mentioned here, the contrast.

You'll be able to differentiate much better the levels of dark or light. So when you are in a night scene or open area with lot of sunlight you'll see better all the elements on the screen instead of what we have today that things get hidden in plain sight due to scene being to dark or bright.

But of course the effect will need both a good panel and content. Some "HDR" panel and content are very light on the contrast ratio.

Of course there is, the luminosity is the main focus for me and trumps all else. Having three different light scoures or more crossing each other in Metro Exodus and one seemingly blinding you yet still being able to see the environment as if through the light rays in Metro Exodus Is crazy cool. I don't know much about colour blindness but surely having bmmore natural lighting scoures with a wider range from black to full luminosity would have to be a boon for the colour blind more than anyone else, No?

Thanks Don and John for your answer.

Yes, as Svennoj experimented in GT Sport for example. I think it's something I can notice, but if I have the good panel and content as you said.

Yes, it's still a better option, I suppose, even if the gain is much less than a person with normal vision. Does the lumen power of a panel depends on its HDR capabilities ?

For explaining color blindness, pictures are better than words :

https://hitek.fr/42/vision-des-couleurs-daltoniens_4682

(scroll down to examples)

In my case, it's a deuteranomaly, and I can't see any difference between a deuteranomaly picture and a normal vision picture.

Thus, about color perception from HDR, I'm not sure that I can see the difference with a No-HDR display.

Thanks Don and John for your answer.

Yes, as Svennoj experimented in GT Sport for example. I think it's something I can notice, but if I have the good panel and content as you said.

Yes, it's still a better option, I suppose, even if the gain is much less than a person with normal vision. Does the lumen power of a panel depends on its HDR capabilities ?

For explaining color blindness, pictures are better than words :

https://hitek.fr/42/vision-des-couleurs-daltoniens_4682

(scroll down to examples)

In my case, it's a deuteranomaly, and I can't see any difference between a deuteranomaly picture and a normal vision picture.

Thus, about color perception from HDR, I'm not sure that I can see the difference with a No-HDR display.

Ya, one could go back but playing games (at least games that aim for realism, TPS and FPS etc) in non HDR, everything is washed out but mostly it's the lighting, the lighting in games is terrible, you have maybe two modes where you wither see bright areas or dark areas and no inbetween. In HDR you see various levels of brightness all in one scene (Like half a dozen or more) with all light scources existing together without canceling each other out or having contrast and black levels raised. Lighting never falters with this tech, not once but in non HDR lighting shifts and alters to accomedate the contrast. Sure I can go back and forget about it, let my brain accustom to old lighting again in the same way I could play a ps3 game but it's a much lesser experience. After Metro my eyes are opened, playing that game without HDR on is like playing Fallout new Vegas compared to fallout 4 with it's terrible lighting indoors. Even with 4k, only after a few months of it, it's so hard to go back to 1080p with all it's aliasing caused by lack of pixels and lack of detail and real estate on screen and I was one saying the difference was minimal the last two or three years. 

Check to luminosity of your panel to see if you are getting the full wallop for your money, My mates computer monitor is HDR and it's a lot less impactful than my TV and then again his QLED TV blows mine out of the water.