> Perhaps I don't know what I'm missing.

I think that's it.

I've used both, and the switch from 16:9 to 16:10 was a regression. Way too much vertical cramping (and other dumb stuff, like fat bezels). I've switched back to 16:10 to the greatest degree possible.

4:3 to 16:10 was an actual improvement, because it gave more space for sidebar stuff. I'm curious if 3:2 would be a better compromise than 16:10, but I haven't had the chance to use a monitor like that.

It’s less of an issue with larger screens, but with small screens 16:9 gets vertically cramped really easily with all of the taskbars, menubars, toolbars, status bars, titlebars, etc eating up that space like candy. Open up an IDE like IntelliJ or Visual Studio (not Code, full fat VS) on a 13” 16:9 screen and this problem becomes immediately evident.

Most devs would probably prefer an ever taller aspect ratio than 16:10 but laptops with those screens that fit other needs are hard to come by.

It’s one of the reasons why I think the notch was actually a net positive on MacBooks: Apple added a strip of vertical pixels to 16:10 which acts as a “nook” for the menubar and notch to live in, making it effectively taller than 16:10.

16:10 is tall enough it doesn't feel like you're viewing your screen through some kind of short fortified viewport-slit.

It's longer, so there is more of the thing visible on the screen. More lines of an article you're reading, more lines of the document you are writing.