16:10 or 3:2 screens usually are not reduced in width (compared to 16:9), but extended in height. For example, the 16:10 counterpart of FHD is not 1728x1080, but 1920x1200. (Historically, it’s actually the other way around: When 16:9 displays were introduced, those were cut-down versions of existing 16:10 resolutions, with the same horizontal but less vertical resolution.)
If you’re used to the extra height, even ultra-wide aspect ratios such as 21:9 (or even wider) do not compensate for the lost height compared to the corresponding :10 or :10.666 height.
It doesn’t really matter, if the diagonal is roughly the same and you use 200% scaling. The corresponding 16:10 or 3:2 would still be preferable (or even 4:3, which was once the standard aspect ratio for laptops). For a given notebook width, you basically want as much height as possible.
For desktop monitors, it can be more of a personal preference regarding FOV and window layout. For me personally, I think a ~30" 16:11 [sic] would be close to ideal.
I math'd this out recently and decided that ~16:9 actually would be the ideal ratio for me.. On a ~42" 8k monitor, using 2x scaling.
I'm optimizing mainly for viewing three documents side by side here. Having your primary document (e.g. text editor or IDE) centered means you're not constantly turning your head one way or another. And it has the added benefit of working well for media (compared to 3 monitors in vertical orientation). At 8k and that screen size.. the aspect ratio doesn't matter as long as there's enough vertical pixels and inches.
I found the same thing when 4k was first coming out on an inexpensive hisense TV. It would be hard to go back to only 2 or 3 side-by-side editing panes.
If you’re used to the extra height, even ultra-wide aspect ratios such as 21:9 (or even wider) do not compensate for the lost height compared to the corresponding :10 or :10.666 height.