dude, you make zero sense: A 4k display has a resolution of 3840 X 2160 (consumer format, UHD). Unless you increase the font size/scale up text is hardly legible. That is one issue;
The other issue you talk about is vector based fonts that scale well with different resolutions and different dpi. Now, the problem to start with is that most apps today do not peruse vector based fonts but most apps are bitmap based. That means to increase the size of text or graphics they need to be scaled up. This is the problem when you now throw an app that is bitmap based on a 4k display. You need to scale up the fonts or graphs or all together in order to read the otherwise incredibly small font size.
If you are saying that you see a difference between a 2560x1600 and 4k resolution when it comes to font clarity on vector based fonts or UI elements that scale well, a difference that you perceive as large enough to spend 2000 USD vs 300-500 dollars then that is your choice of course. I am sure there are people that swear by 20,000 usd audio components that a normal human being cannot perceive any difference between such and a 200 dollar component.
But fact remains that unless your fonts or UI are purely vector based you MUST scale up to increase font size or the size of graphical elements. And then you end up with unclear/blurry content and eventually the same real estate than a display with a lower resolution. I still claim a 27 inch or even 30 inch 4k display is total nonsense. But hey, I heard your story million times before. When people swore by the new Retina mobile phone displays I already thought that was a totally ridiculous claim. Now the same story with slightly larger displays that people stare at from a 50cm distance. I do not know Apple space and could not care less (given most Apple enthusiasts all run Windows VMs anyway begging the question whether they just need to show off hardware or are actually dumb enough to switch between the Windows VM for app use and then Mac OS so they have bragging rights to browse internet on a Mac), but fact is Windows and Windows apps are not ready for 4k displays until all fonts and graphical elements are vector based.
By the way, research has shown that the human eye can recognize only up to 150 dpi from a distance of 24 inches. That is what a 28 inch 4k display offers (meaning any smaller displays, 27 inch for example at 4k make no sense at all). Hence my whole talking that I do not think we will see much higher res displays in the future.
Take a look at this report (I think it is independent and quite honest, make sure you do not miss the "conclusions" section: (July 2015 report)
https://pcmonitors.info/articles/the-4k-uhd-3840-x-2160-experience/#!prettyPhoto
I do not even know why we discuss back and forth do a google search mate, many people clearly disagree with you:
https://www.google.com.hk/webhp?sou...&espv=2&ie=UTF-8#q=windows+4k+displays+blurry
https://www.google.com.hk/webhp?sou...v=2&ie=UTF-8#q=windows+4k+does+not+scale+well
https://www.google.com.hk/webhp?sou...ion=1&espv=2&ie=UTF-8#q=windows+4k+eye+strain
Completely false man. Have you ever used a Macbook Pro Retina? Try using one and then try using a non-Retina and you'll immediately see what I mean. 200+ ppi displays are not only very sharp but the OS is distinctly aware of this and fonts are rendered appropriately. Font size doesn't even typically change - just more pixels are used for the same space resulting in higher resolution. Of course many people, including myself, run the things at max resolution to reduce the size of UI elements giving us more effective real estate while still retaining clarity.
Windows 10 will get it's act in gear eventually - but until then people can run Windows 7 or figure out work arounds to make things look sane. Or you could just do as I said before and run a Fusion VM with Windows 7 and have MacOS for non-trading stuff. Great combo IMO.
