I'm personally on the old 30" 16:10 2560x1600 form factor, and it's wildly better visually than the 27" 1440p screen by the same brand (all of them Dell) I use at the office.
I have an 24" 4K Dell I bought when big 4k screen with good (measured) colors were still expensive. It's a very pleasant screen to use. Sure, it has less real estate than a bigger one, but this is somewhat mitigated by the fact that I can keep it closer to my eyes, so I can use smaller text.
I find it makes me more "focused" in a way. Can't have multiple windowfuls of crap visible at the same time. It's very practical for TWMs. It also works well in a dual screen scenario, for stronger separation when you need it, but I'm still not sure if a single bigger screen is better than two smaller ones for things like having docs up next to code for example.
I find I can't use two 27" or higher screens, they're just too big and I need to turn my head way too much for comfort. At work we have a 2x27" 4k setup, and I basically only use the screen in front of me. Later I've been experimenting with pushing them very far away, but then I just need to increase text size and lose actual real estate.
> but that just seems ridiculously small considering how available larger displays are for the same ppi and refresh rate probably
I don't particularly care about refresh rates above 60 Hz (my laptop does 120 Hz, can see the difference, don't care). But I do care about PPI. Which screens are easily available with the PPI of a 4K 24"? I'd expect something like 5k 27" or 6k 32". These are very expensive (>1000 € for a crappy 27" Samsung, 2000 for a 32" Dell) and not that common, at least in France.
I feel basically the same way, and I don't like excessively wide screens or even 16:9. I've always preferred 16:10, and have wavered between 1,2,3 screens over time. 16:9 27" 1440p is not a pleasant form factor, but it's fine in vertical mode.
I tend to prefer PPI, but not at the cost of screen real estate, and I tend to prefer 120hz, but not at the cost of PPI or picture quality. So the Dell Ultrasharp 30" series from years ago, with IPS 60hz and 2560x1600 is perfect for now, and it also lets me run games without investing substantially in brand new gaming PC hardware. The picture quality is great, the price on the used market is great, screen real estate is great, it's just not as sharp or fast as my Mac screen.
I've got my eyes on 32" 6k displays, but since they're so ungodly expensive, I'd really prefer them to have 120hz and good HDR, even though they're not priority attributes for me. I'd keep one of the 30" displays next to it in vertical mode for documentation or log files
I sorta wish that form factor had taken off instead of 27" 1440p. The extra vertical space is really nice, and that seems to be the ideal PPI for 100% scaling IMHO.
I keep telling myself I'd like to get a 4K OLED display at the same PPI, but 40" seems to be conspicuously missing in every monitor lineup... at least at a price that will convince me to buy three of them, anyway.
I think the largest I would want at my current desk is 27". 30 is way too big for me. But more importantly I want something that matches the crispness of the MBP display, and 1440p and 1600p are too low res.