Simple question:

Monitor.
16:9 or 21:9? What do you prefer?

Fell free to write pros and cons :D

21:9 or the 31:9 (I think it is 31)

Multiple 16:9, practical and persuasive.

16:10 in portrait. Widescreens and extra-wides are good if you're a designer or artist. Anyone who writes should be using a portrait monitor (or several) and the extra width from a 16:10 is a massive improvement over a 16:9.