My 11 inch asus laptop has a full hd display. So it's somewhere in the middle.

Gnome's hidpi support doesn't allow float values, making this a serious issue to me. On top of that, you'll have to change the cursor size manually by diving into the config.

The iphone 6+ display uses downsampling, so perhaps that's the way to go. But as things stand, I don't see my self using an external monitor in the near future, even after wayland becomes mainstream.