Github + Travis CI for public repositories. Gitlab + Gitlab CI for private repositories due to cost-benefit

here is a great blog post written by Fabio Akita: Moving to GitLab! Yes, it's worth it!

GitHub straight. Only for private repo go to other options: bitbucket/gitlab/... as per requirement.

Github for open source, gitlab for private repos (because it's free).

I use both, github 'cause that was the one I first started to use and gitlab I use at work and also on work I want to make private without paying.

I personally use Bitbucket when I need some private repositories (customer projects) but as I'm a huge open-source fan, github all the way !

gitlab for my commercial customer projects and github for my opensource projects :)