Dave -- please, let's not re-live 'tar-wars' -- it's why the POSIX command is called 'pax' - God Bless USENIX for funding the original implementation and putting it in the public domain.
- tar was research/BSD and worked best when you chdir to some directory and were working interactively and was the logic follow on to the earlier stp and tp. It was ASCII and after the binary issues of tp was a welcome relief. The format was also extensible (thanks to bug in the original implementation).
- cpio was USG and worked best with a find(1) script/automation - which was good for controlled distributions but poor for interactive use. It was also binary originally (with PDP-11isms builtin)
The real issue in the end was cpio being part of System III many/most universities did not have it originally, so the tp/stp was what we used, which was replaced by tar.
pax has a user interface that work either ways, and the USENIX public implementation can read both tape formats..
Clem
PS At Masscomp, I once wrote "car" but no one ever wrote "tpio".