@BeKind, I'm certainly aware of the fact that beyond a certain distance vs screen size the human eye cannot perceive the difference in pixel density (detail). But I'm not even talking about that. I'm simply comparing 65" to 75". Above a certain threshold of picture quality, the overall experience and immersion will simply be better and more enjoyable with the larger screen, even if you sit proportionally closer to the 65" to even out the perceived screen size.
Why? Because our brains form a complete understanding of context based on far far more than just the distance between our eyes and the screen (size). We get cues from the environment, size of the stuff on the walls, doors, windows, furniture, light fixtures, the cup in our hands, etc. that our eyes always pick up on. Even in an otherwise "pitch black" room the screen itself throws off enough light that we pick up on these cues.
But of course between 2K and 4K within a certain distance you can perceive the difference. It's why I'm ultimately getting a 55" 4K for a different spot at which we sit much closer to the set. I'd go larger but it wouldn't physically fit.
As for the differences in picture quality between the various levels of Samsung sets, you're kidding about asking F8000 owners I assume. Talk about selection bias!
Regardless, note that I explicitly cited the *only* differences in picture quality between the levels, and that these differences can be seen. I know because I've seen them myself and when correctly set up are not particularly difficult to discern. That doesn't make the differences anything more than marginal however.
I also noted correctly that these features bring with them other performance issues of their own. Just ask 7100 and 8000 owners
The threads are littered with complaints about the dancing white boxes tied to the cinema black feature, which for most owners can only be used successfully at the low setting (ie its least effective - gee thanks Samsung) or the inconsistent picture dimming owed to the smart led setting in the 8000, which again is usually engaged in the low setting to minimize the issues it causes (again, thanks Samsung!) And if a user doesn't notice these problems - both easy to see - then I question how discerning they are as viewers, and therefore whether they ought to be spending way up the cost curve for marginal picture improvement, regardless of their particular socio economics.
Again, all are obviously completely entitled to spend their funds as they wish (duh) but history has shown us time and again where on the price/performance curve we're most likely to get hurt the most. Some choose to ignore this - great (and thanks for living on the bleeding edge and bringing costs down!) - but there is no harm in making absolutely sure people understand this.