I tried to explain in your other thread in the CIH forum that there is size and there is Aspect Ratio and the two do not go hand in hand making the most pleasant viewing experience for me.
The term is immersion and here is an example.
Schindler’s List is a 1.85:1 movie sometimes called flat AR.
The Aeronauts is an IMAX movie 1.89:1
The Nightly News with David Muir is 1.77:1 and is TV
The Super Bowl is also TV and is 1.77:1
These four things are so close in AR that it is hard to tell one from the other when just viewing the rectangle shape, but the sizes of those rectangles can be greatly different and equally as comfortable to watch do to how they are shot. That is because of the cinematography used.
The nightly news is not made better viewed as large as an IMAX action movie. Schindler’s list was never intended by the director to fill an IMAX screen it was intended to be as tall as a scope movie 2.40:1 and shown in a scope theater. Some (myself included) will say there is merit in watching the super bowl larger than CIH would allow and larger than the nightly news.
Steve is correct there is nothing wrong with showing everything as large as you can if that is your thing. Movie theaters have rows and rows of seats and if you sit in the front row or the back row the change in immersion more than covers that CIW range.
So it boils down to personal preference as it is your personal theater you are building and you only get one or two rows to pick from at home.
I don’t think 2.4:1 is going away, and I also don’t care what new ARs they come out with. My projector is 16:9, the media I watch has a max capacity of 16:9 be it disc or broadcast or streaming it is 16:9 max filled in with black bars where they don’t have image to fill it. So it is simple for me I need a screen that has a 16:9 area large enough for the largest thing I would ever want to watch both in width and height and I need a projector with enough zoom to go from that to the smallest thing I will ever want to watch. As long as I have those two points let Hollywood or Netflix or whoever throw whatever they want my way and I can watch it how I want.
I just watched Da 5 Bloods the other day and it would have drove anyone trying to control presentation nuts as it jumps around between 4 or 5 ARs in different sizes. I knew parts of it were 2.4:1 scope and some of it then was IMAX-like 16:9 so I zoomed out and let it rip. I didn’t really care for the movie but the presentation was fun.