Interesting although I'd have liked more summaries: there's an awful lot there.

But the reasons I choose filesystems are more about reliability, failure modes, surrounding tooling, and so on.

Btrfs fails in several critical areas:

1. No way to accurately find free space

2. catastrophic failure on write if a volume fills up, the probability of which is greater because of #1

3. repair tools usually do not recover a corrupted volume and in my testing are most likely to render as damaged volume completely unreadable, which makes #2 worse

Put these things together and I can never trust Btrfs again. In the 9 years since I encountered these, I see no effort to fix them, just fooling around witg unimportant side details like performance tweaks.

Fix the critical issues first then make it faster.