What I noticed moving from landscape to portrait and back is that 16:9 is really, really flat, like you don't think about it every day as you are used to this but it's absolutely cramped vertically!
It doesn't affect as much the portrait orientation that should look narrow, instead most content aside for videos and games fits perfectly, with tons of visibility without scrolling say on documents, folders or web.
4K with 16:9 doesn't really solve the issue as you get excess of pixel density in a narrow screen, resulting in the need of text scaling to read any comfortably.
To get the best of both worlds there are some 1920x1920 panels… I think only Eizo sells those, they cost over a grand but I'm really tempted to get one and enjoy it for years. Till some ludicrous 3840x3840 gets its place!
