Based on my own experiments, lzip can produce smaller tarballs than bzip2, and they’re quicker to decompress. (This is based on the distributed dhall-1.29.0-x86_64-linux.tar alone).
There’s some more info here: https://www.nongnu.org/lzip/lzip.html but the gist of it is: lzip is designed for archiving (it has better error recovery) so it would make sense to keep some such archives around!