ORG's tightly integrated into emacs & it's ecosystem. It's fine but I don't think there is an equivalent to Sphinx for large cross referenced documents, with different outputs formats & support for translations (different languages).
Perhaps some of these things exist - I may be wrong, if they do I doubt the system is as mature or well supported as Sphinx's.
Perhaps some of these things exist - I may be wrong, if they do I doubt the system is as mature or well supported as Sphinx's.