Who uses a browser in full screen? The browser is typically, as fas as I can see, run as a window with other stuff down the sides. And that's something widescreen grants, and why super widescreens are still valuable. You can open multiple portrait documents side by side. A massively portrait screen could open multiple documents one on top of the other, but it's hard to view up/down than left/right, so I think widescreen wins the ergonomics argument. In complex apps with lots of tool panels, widescreen lets you run them down the sides, perfect for lists.
I don't see any real benefit to narrower aspects, excepting the first case. At the end of the day, aspect doesn't really matter when content is windowed, leaving full screen content as the deciding factor for best fit aspect, and that's chiefly movies and games.