Nothing so complicated as suggested below, re photography.

I simply want the absolute maximum screen space that I can use one handed. that makes elongated aspect ratios more useful than square ones.

unlike tablets, which are two handed devices so the importance goes back to the viewing utility which favours square screens.

i'm a big fan of the new breed of 6" 18:9 screens, where previously i've said 5.2" was as big as i could comfortably use one handed.