You can choose only one mainstream social media, which one would you pick?

I've been trying different social media lately, surprisingly there's quite a contrast in the users, LinkedIn has an overly supportive crowd, Instagram has an overly rude and mean crowd. Haven't been much on twitter so still making my mind on it. Each platform has their own problems, and has their own share of cringe. If you were to use only one social media forever, which would you pick ? Grapevine is an obvious choice here so not including it in the poll.