Less viewing angle, typically, but usually that's not a great concern.

And on-topic, of course, we're talking sufficiently narrow screens that width is not necessarily wasted, and laptops would look funny with portrait screens, but you said off topic, so I understand you're talking exclusively of desktops.

Buy 2? stack 'em! Dual monitor rigs don't have to be wide, ya know.

But I don't really care (for desktops) what aspect ratio; I'll throw my apps around to fit.