Before you think of switching to GitLab, look at their status Twitter account over the past few months. They've had a lot of down times. They run on Microsoft Azure.
What does this have to do with anything? Are you suggesting that service run on Microsoft Azure are not stable?
The downtime of GitLab.com is something the team are committed (see https://about.gitlab.com/gitlab-com/ - 'Disadvantages') to improve this year.