I'll go one step further: I used the LG 27" 5K Display for two whole years before returning to a 34" Ultrawide with a more typical DPI.
Obviously I preferred the pixel density and image quality of the high-DPI screen, but I find myself more productive on the 34" Ultrawide with a regular DPI. (FWIW, LG now has a newer pseudo-5K Ultrawide that strikes a balance between the two).
I look forward to the day that monitors of all sizes are available with high DPI, but I don't consider it a must-have upgrade just yet.
Also Note that Apple made font rendering worse starting in OS X 10.14 by disabling subpixel AA. Using a regular DPI monitor on Windows or Linux is a better experience than using the same monitor on OS X right now. If you're only comparing monitors based on OSX, you're not getting the full story.
I also have 3440x1440 on my Dell monitor at home, and I love it.
My work monitor is a really nice 27" 4k LG monitor, which a coworker picked out. He's a real monitor specs nerd and made a lot of assertions like the OP. The scaling issues are endless and really bother me, and I don't notice the higher PPI at all. I much prefer the ultrawide Dell - it gives me a feeling that I don't even need to maximize my windows and I can still have lots of space.
It takes up zero desk space (one monitor arm that lets me adjust it anytime I want), and I don't need to rotate it. I've never found that a useful thing to do.
On the other hand, when you're done work its amazing for flight simulator or other games that support the aspect ratio properly.
I'll go one step further: I used the LG 27" 5K Display for two whole years before returning to a 34" Ultrawide with a more typical DPI.
Obviously I preferred the pixel density and image quality of the high-DPI screen, but I find myself more productive on the 34" Ultrawide with a regular DPI. (FWIW, LG now has a newer pseudo-5K Ultrawide that strikes a balance between the two).
I look forward to the day that monitors of all sizes are available with high DPI, but I don't consider it a must-have upgrade just yet.
Also Note that Apple made font rendering worse starting in OS X 10.14 by disabling subpixel AA. Using a regular DPI monitor on Windows or Linux is a better experience than using the same monitor on OS X right now. If you're only comparing monitors based on OSX, you're not getting the full story.