I've always found these debates about what is the one true superior ratio a bit weird. It depends on the specific application. And by application, I don't mean anything as broad as "multimedia editing" or "office work" - I mean, it depends which specific task you're trying to carry out, what program you're using, and how you want to configure the layout of that program. Chances are you carry out a variety of different tasks throughout your day, and each one would benefit from a different ratio. Some documents/content/media are tall, some are wide; some programs have top bars, some have sidebars.
Writing or reading a long article, or programming? you'll probably want 3:2 or taller.
Spreadsheets? Well it would clearly depend on the format of the documents as these can be oriented either way.
Graphics program with a sidebar? 16:9 or 16:10 is good.
But with any of the above, if you want programs side-by-side e.g. reference material next to working document, 21:9 would be better.
And there are not many lines of work where you'll be limited to a range of tasks that all have the same ideal ratio - chances are you'll be switching between tasks where you'll want a wider screen and tasks where you want a taller screen. Compromise is the name of the game.
But the difference between 16:9 and 10 is minuscule - depending on how you look at it, a 11% increase in height or a 10% decrease in width (in resolution terms, I expect it to always be the former - otherwise we get 3456x2160..)
As an architect, I use a lot of 3D and graphics programs, plus the occasional excel or word, and it's not unusual for me to want to split my screen. If I get the XPS, I'll be very happy about the extra 240px height, but if someone offered an extra 400px (or whatever) in width instead, I would be just as happy.
The solution? a screen that unrolls. extra height or width, whenever you need it. one day...