I’ve found that if you use Twitter mindfully, it can be a pretty great platform for meaningful conversation. The trick is to only follow a handful of people you find particularly interesting, and ignore the trending stuff. I fall off this wagon pretty often, I’ll admin, but I’ve had a ton of great discussions there that I’ve gained a lot from.
I’ve mostly dropped Facebook entirely. I just mirror some of my Twitter posts there, and occasionally follow up on comments, but I don’t read anything on Facebook at all.