Different networks for different purposes.
It all depends on what you want from each network...
Chatting to a friend in Poland (she uses FB Messenger almost exclusively to talk to everyone, so I have no choice).
Trading banter with colleagues and casting doubt on their sexual preferences (human, animal, vegetable etc).
Using my profile to log into sites that require it, such as Spotify used to.
Decent, intellectual, conversation with like-minded people and groups.
A much, *much* better cleaner interface.
Massively better mobile app.
As G+ are now rolling out site/app authentication using your G+ account, that's one less thing to use FB for - pretty soon it'll just be for chatting to my Polish mate and nothing else, and at that point, I'll probably consider just closing my account or stripping it bare of all personal info and using it as nothing more than a glorified MSN Messenger.