I use both: I stick my private repos up on Bitbucket (where I don't need to show them to anyone, and thus pay nothing), and my public repos on Github (where I don't need to hide them from anyone, and thus pay nothing.)

And I don't miss Github's collaborative features in my private repos because I'm not collaborating in those :) Bitbucket is literally just "a place to push my repo where it'll be safe" for me[1]; Github is "a place where I can collaborate with others."

And you know what? You can even use both for a single project. Push your public branches to Github, accept patches, then base a private product on the result [just some extra non-pushed-to-public branches] and work on that in Bitbucket. For example, you could have, say, the Chromium codebase on Github, and then Chrome on Bitbucket.

[1] Well, okay, Bitbucket is also pretty good for doing deploys from: you can CNAME git.yourcompany.com to them, set up some Deploy Keys and Deploy Hooks, and it'll feel just like you had your own internal repo server for your deploy server to talk to.