https://github.com/mpv-player/mpv/wiki/FFmpeg-versus-Libav gives an interesting perspective. Libav sounds like it's strict about good software practices and merciless in its exclusion and deletion of "bad" code. This may make a cleaner, more sustainable product over the long term, but it makes compatibility a nightmare now, which is probably why distro managers are increasingly interested in swapping libav back out. Perhaps if they had a more steady, formal release cycle it wouldn't be annoying and they'd have been able to maintain their position in the distros they got to carry them (I think almost all of them have reverted to ffmpeg as the default now). Since libav aggressively deletes old stuff and painstakingly reviews each patch (according to this article, no direct experience), they don't merge a lot of "new stuff" from ffmpeg.

ffmpeg has maintained compatibility, making it really easy for downstream users and distro maintainers to keep going, whilst continuously adding new features and improvements, including aggressively merging those placed in libav (I guess as long as they aren't deletions or cleanups?).

I feel like there's a lot to learn in this whole drama and that it hasn't been very deeply explored. libav team originally claimed that ffmpeg's leadership had gone dark/fallen off the map, but they sure came back quickly to express discontentment at the mutiny. libav team undoubtedly has talented people working on it (wasn't DarkShikari on the libav side of the schism?) and libav/ffmpeg share a lot of goals. You'd think they could come to some type of compromise less onerous than this entire saga has been. IMO it's a failure from all sides that this fork was even a thing. A phased, unified, slow, and well-managed release process like Python 2 -> Python 3 might have made all of this unnecessary.