Which package to upgrade psql client?

If you've installed the new server, the new clients are installed too - they're a dependency of the server.

Redhat systems now use an "alternatives" mechanism similar to Debian. You'll find that /usr/bin/psql is a symlink pointing to /etc/alternatives/pgsql-psql which is in turn a symlink to the default psql.

You can use the update-alternatives command to switch default clients - see its --help. Or you can just:

/usr/pgsql-9.3/bin/psql

directly.