RCS is basically a modern evolution of SMS. It's an open standard, but by far the biggest implementation is from Google on the client and server end. The mobile carriers really never got their shit together.

The downside is that there is no public RCS API on Android like there is for SMS, and Apple doesn't support it.

No encryption for group chats, but that has been changed and is encrypted.

Less features than the other messaging services, like Whatsapp, Messenger and more.