32" 4k monitor at a normal viewing distance (~30" seems like a good estimate without bringing out a measuring tape) is pretty comfortable for work at 100% scaling. At that distance 1080p video looks significantly worse when compared to 4k, although a large chunk of that may be due to bitrate.
Right, va for 1080p is something like 3.5' for a 24" monitor. Most people will be able to see a diff between 4k and 1080p, but I'd imagine 4k vs 1440p would be negligible.
