Quick answer. RCS reaches customers in their phone’s built-in inbox; Facebook Messenger reaches only people who use Messenger and have connected with your business there. RCS needs no third-party app and falls back to SMS, giving broad, low-friction reach with verified branding. Messenger can be effective for brands with an engaged Facebook audience and supports rich, conversational flows, but its reach is tied to the Meta ecosystem and a customer’s presence on it.
Choose RCS for native-inbox reach independent of any social platform; choose Messenger to engage an audience that already interacts with you on Facebook.