ext4 is consistently faster for storage node uses than btrfs, even when you strip btrfs from all the features that make it better than ext4. I’ve run tests in which I replayed the exact I/O performed by a node. btrfs took twice as much time to run it and was 3-4 times slower at performing the file walker process. btrfs for storage nodes sound like a good choice if you want your drives to die faster.
No idea about zfs though, I haven’t measured it.