Published very recently by Phoronix, a series of benchmark tests.
Don’t look at any one page in the tests expecting to see a result that might suggest one file system is better than another,
After stepping through all pages in an article, it’d become apparent that each fs might perform better running certain tests.
Each of the following articles are tests on a different hardware platform, the first link is the only one for single disk.
Each of the others describes different RAID configurations.
One thing that seems to be true for BTRFS in all three articles…
For whatever reason it seems to be much slower initially starting up stuff, eg during a boot and launching an application, but otherwise can perform well.
Linux 5.0 File-System Benchmarks: Btrfs vs. EXT4 vs. F2FS vs. XFS
Linux 5.4 EXT4 / XFS / Btrfs RAID Performance On Four HDDs
Linux 5.5 SSD RAID 0/1/5/6/10 Benchmarks Of Btrfs / EXT4 / F2FS / XFS