[petre]

I did some tests of my own and xz turned out marginally better than lzip in most of them.

    665472 freebsd-11.0-release-amd64-disc1.iso
    401728 freebsd-11.0-release-amd64-disc1.iso.xz 5m0.606s
    406440 freebsd-11.0-release-amd64-disc1.iso.lz 5m43.375s
    430872 freebsd-11.0-release-amd64-disc1.iso.bz2 1m38.654s
    440400 freebsd-11.0-release-amd64-disc1.iso.gz 0m27.073s
    431740 freebsd-11.0-release-amd64-disc1.iso.zst 0m3.424s
    

Maybe xz is not good for long term archiving but it's both faster and produces smaller files in most scenarios. However, I'm sticking with gz for backups, mainly because of the speed and popularity. If I want to compress anything to the smallest possible size without any regard for CPU time, then I use xz.