Plus the GitLab team has just been killing it with each release, and it just feels good to use open source (and be able to open issues, vote on improvements, track changes for the upcoming release...). Free private repos is just icing.
Setting up a project for both just takes a few initial commands to configure git:
git remote set-url --add --push origin git@github.com:account/repo.git
git remote set-url --add --push origin git@gitlab.com:account/repo.git
Then pushing to origin will always push to both. I also add a github and gitlab remote in case I only want to push to one as well.