Ted Ts’o sent out the EXT4 updates today for Linux 6.11. He explained in that pull request:
“Many cleanups and bug fixes in ext4, especially for the fast commit feature. Also some performance improvements; in particular, improving IOPS and throughput on fast devices running Async Direct I/O by up to 20% by optimizing jbd2_transaction_committed().”
Ext4 is not legacy, just because something newer is out there. Ext4 is proven and rock solid, not without reason the standard for most Linux systems. It doesn’t randomly corrupt your files. If someone would read your reply, one would think that Ext4 is abandoned since decades and a risk to use.
If one has to ask and don’t understand Btrfs, should just use Ext4 by default; a safe and good option without risking anything. There are no downsides to this. Use Btrfs only, if you know what you are doing, if you understand it and actually need the extra functionality.
And, may I add, if your chosen distro defaults to it.