As I posted in that other thread... When working, I typically split it into thirds (so mostly portrait mode for each application). And this is the key advantage for me:
With multiple monitors, you're confined into smaller, "hard-coded" boxes that can't be changed. With a single large screen you have much more flexibility.
At home, I've been using a 28" 4k display with sometimes a laptop display on the side (other times just a desktop driving the display).
As an experiment, I just ordered an LG 43UD79-B (43" IPS monitor) to replace my 28" and also serve as my entertainment. Previously I had a 32" TV and a 50" in another room. I got a lot of good feedback[0]. I'll try mostly just using the middle of the screen with a window manager that makes it easy to do.
Psychologically, it is common to 'Max' the window. With one big monitor it becomes an issue. But like I said above it is more of a management issue.
If you can sub your screen into 4, not overlapped windows, without much work, then one big one can work.
The bezels do not bother me, usually because I usually do not have a window spanning 2 monitors.
I have set up a monitor vertical. Typically when doing 'new' code, or writing a document. Not so much when debugging or editing. And it is usually just one of the monitors. Other(s) are set normally.
You can do that with one big screen and a good window manager, but the effect may not be the same.
One extra monitor is good enough for most people, but to each his own. The downside is of course, it's not the most minimal setup. But when you're in the zone, you don't care about the aesthetic anyway.
The bezels are completely irrelevant; I never notice them at all.
I use two setups:
Work setup: 13" laptop and 24" monitor in portrait. External monitor displays only tmux in full screen.
Home setup: 15" laptop and 29" monitor in landscape. The monitor is the de facto main screen, I only use the laptop one for recording or browsing while gaming.
I'm intrigued by super wide monitors. My desk currently doesn't fit one though.
I prefer two identical monitors next to each other which works well for multitasking with two different applications, eg IDE + safari. In this setup, the bezels help separate the contexts for each application. However two monitors don’t work as well for one single application spanning between them, eg giant Minecraft.
Using multiple monitors come as a merit when someone needs to have multiple windows displayed at all times.
I think one way you can make this by using a single screen is to use a tiling windows manager.