Which one to choose? RHEL HA Add-On or RHEL RS Add-On?

Just wanted to request for information on what specific things do I need to look out for to determine if my client needs HA or RS Addons.

Which one do I need for A/P clusters and which one do I need for HA clusters?

Also, may I please know if there's an in-depth comparison between the two?

Thank you!