GitLab allows unlimited private repos for free (that's the main reason)
This means our code can be hosted at home, not on a foreign server.
GitLab has integrated CI service (no third-party involved)
GitLab is open source!
GitLab CI (on
gitlab.com) is faster than Travis CI to trigger, has less limitation (build time limit for open source projects = 60 min on Travis CI if I remember correctly, you can bypass that limit for free on GitLab).
In terms of functionalities they are very similar, I would say GitLab is a little bit superior than GitHub but for what I use they really are equivalent.
I am migrating my projects to GitLab and will keep the GitHub repositories as passive mirrors.
I'll keep some GitHub repositories like Bezier for example because the official repository is on GitHub and we can't pull/merge request between GitLab/GitHub (yet?)