For development I take screen real estate over PPI. The idea is to run it at native resolution while being very readable, and to be able to work on multiple documents side by side.

(And for coding you actually need height more than width, if you think of a typical layout of a code file)

To each their own. I love the fact that I can't see pixels on my retina iMac at 220 PPI. It makes reading code much nicer.

I still have more than enough room for a few buffers on screen.

I agree with you. I'd love to try a 4k screen, and was even considering it - however in the end I took my home U3415W to work and bought the X34 for home (I might game 30 minutes a week or something; the extra hz are certainly nice for that, otherwise they are pretty much identical).

I value actual real estate over PPI, preferring to run at 100% / unscaled which looks much nicer in Win10. The 109PPI (3440x1440) is decent enough, and I don't have to squint. Furthermore the DPI matches those of the surrounding 16:10 24s (1920x1200) well enough for it not to be an issue.

Not arguing against that, however Visual Studio has lots of windows eg NCrunch runner, output, solution overview in addition to editor(s).

The ultrawide allows for this nicely; tests on the left, two actual editors, solution explorer on right, and output at the bottom under the editors.

Do you mean 9pt or 9px font? Either way, that's not comfortably readable on a 32" 4k screen.

On a 34" 3440x1440 screen I keep IntelliJ at 14px (10.5pt). On a 32" 4k screen I keep it at 15px-16px (~11pt).

You're still only talking ~100 lines of code on the screen at any one time. Maybe ~130 with a smaller font.