There definitely exist certain kinds of data which xz can compress better or as well but faster than zstd, even taking into account the more extreme compression

There definitely exist certain kinds of data which xz can compress better or as well but faster than zstd, even taking into account the more extreme compression options offered by zstd. I know because we have many terabytes of such data, and I've done thorough comparisons between xz and zstd at all different compression levels. However in all cases zstd is much faster for decompression. It just happens that getting the best compression ratio in a not insane amount of time is still the better tradeoff for us.