I've experimented a bit with bzip3, and I think the results in the readme are not representative. I think it's a handmade pick, with an uncommon input and unfair choices of parameters. And it's made with a HDD, which skews the results even more.
For instance, with a 800 MB SQL file, for the same compression time and optimal parameters (within my capacity), bzip3 produced a smaller file (5.7 % compression ration) than zstd (6.1 % with `--long -15`). But the decompression was about 20× slower (with all cores or just one).
I'm not claim my stupid benchmark is better or even right. It's just that my results were very different from bzip3's readme. So I'm suspicious.
Using the results from the readme, seems like bzip3 performs competitively with zstd on both counts.