In an ideal world, I’d use a 16K curved screen that emits studio grade sound from its very surface - but there are two problems with that:
- Curved screens! Not an issue in most applications, but as someone who suffered through the CRT age, longing for a non-rubbish screen that could show straight lines, I’m not a fan of curved screens.
- This technology doesn’t exist yet!
So, I use flat screens. One 40", one 49" (to be replaced with a 55" at some point), and two 27" ones.
I could theoretically fit slightly bigger screens where the 27"ers are, but 3x40" would start to interfere with stuff. (The front 40" is actually slightly below the desk surface, to minimize interference with the speakers.) Also, the 27+40+27 setup is already wide enough that I’m almost hurting my neck when viewing the utmost areas, so that’s around the point of diminishing returns. Any wider, and it would be better to use more virtual desktops, move windows around or something.
One advantage with the 27+40+27 setup is that the 40" is much taller than any ultrawide screen, which means more tracks without scrolling, or comfortably viewing the piano roll along with a bunch of tracks, and things like that.
There’s also another thing to consider when going to very large screens. “Mainstream” window managers (especially Windows, before 10) tend to be anywhere from unhelpful to outright brain dead when it comes to managing large screens, and you end up having to manually scale and position every window of any application you use, as “fullscreening” a window (other than the DAW main window or similar) is basically useless. Even now, window managers tend to only do side-by-side split, and possibly 2x2 matrix, sometimes allowing you to move the “split” in a smooth manner. If a window spanning half of the screen is still ludicrously wide, you’re out of luck, and will have to go back to the Win3.11 way of window management, or use a third-party window manager or something.
Now, with multiple screens, you have a bunch of natural divisions of the desktop and most (even Windows, as of recent Win10 builds!) can do the side-by-side and 2x2 per screen, activated by the edge of any screen; not just the outer edges of the desktop. In some cases, you can even have actually fullscreen applications (like games) running on one screen only, while the others still show other applications.
Note that I’m only familiar with Windows and various Un*x desktops, and I only have a vague idea how OS X deals with all this, as I’ve pretty much only seen others use it with multiple screens.