[illiarian]

It is, of course, neither.

The most feature-complete and flexible GUI framework is one that is:

- flexible. The web is anything but. You can read, for example, how Figma struggled and how inflexible the web is here: https://www.figma.com/blog/building-a-professional-design-to...

- feature-complete. Once again, there's a reason all UI projects for this "most feature-complete framework" keep reinventing the most primitive controls. Because the web has none, and creating complex controls is a near-impossibility. Also, if it was feature complete, https://open-ui.org/ wouldn't exist.

If you are actually looking for a flexible feature-complete GUI framework, then it's Qt.