Personally, I am very much not on board with RCS at all. But if I had to choose between RCS SMS and anything by Facebook et al, I'd learn to tolerate RCS.
However, as I said, this wouldn't be a dealbreaker. I wouldn't like using it as much, but it would still be better than nothing.
Also, it works without a data connection.
This is why FB chat, whatsapp, etc will never gain the traction that these services do -- putting time and effort into making them work is just a fool's errand until they open up the network to third party clients and make the specs an open standard.