pkexec vs runuser

pkexec is not installed by default on Debian unlike runuser which is. So far I've been using pkexec but discovered there is also runuser, and since runuser seems to be more advanced (looking at options in man entry which I don't fully understand and didn't use the command yet) so this made me think whether there is any benefit to install pkexec since runuser is already there. What pros and cons does runuser have compared to pkexec?