Previously dual monitor, 24" 1920 x 1080, portrait left, landscape right. left was usually for email and chat, right for coding and browser.

Now it's a single 40" 4k tv as my display. Using gridmove to easily partition the screen as needed. It's like have 4 1080p screens with no border. Only downside I've come across is some screensharing apps will always share the entire desktop when sharing a single app (webex is worst offender) - just the app window will be shown, but with massive greyed out background. Can be fixed by changing desktop res, just an annoyance.

Moving to a single massive screen has honestly lead to better productivity, but i possibly attribute that more to gridmove than overall screen real estate.

Only one input on this specific monitor can do 4K@60Hz, all the others are 4K@30Hz or good refresh at lower resolutions.

Takes 20 seconds to enable the second display in display settings and then pick the right input for the PiP mode on the monitor (it has a remote). Most of the time I have my personal laptop displaying in the PiP frame lower right. The remaining 3/4 of the screen is my work area.

This was in the living room, which is sort of inconvenient. So I decided to get one for my desk. Being a silly project just for myself, I didn't want to splurge on it, so I went for the cheapest 4k I could find. I think it may have been a store brand.

The response time on that thing was noticeably terrible, like I would lose track of the cursor in vim because it wasn't keeping up properly.

The moral of the story I think is that you can get a not-terrible 4k tv for coding reasonably cheap, but the response time issue may still exist. It is probably just a roll of the dice.