I used to use iostat to monitor device utilization but now I don’t bother and just choose based on use case. Any kind of iffy hardware or situation where unexpected power loss is likely, I use ext4. It’s robust af. Do I need multi-drive volumes and high availability? Then its ZFS. Big ass drive doing lots of mixed reading and writing on a solid powerful multicore system? XFS all day long. Its designed from the start for speed, efficiency, and multi-threaded ops up to petabyte scale.