For me, it's the highest resolution that my eyes can handle. Currently, QHD ( 2560x1440 ) on a 27" monitor seems to hit the sweet spot. 4K at that size is already starting to strain my eyes. When it comes to laptops, I used to love toting around 11" versions, then 14" and 15". The 15" was 4K, but, over time, my eyes could not handle that. Now I'm 17" at 2560x1600. With the two monitors offered above, I would go with the 3440x1440.