All those sites are secure. Actually, between the three, GitHub has had the most vulnerabilities reported, like that one time someone got administration privile

All those sites are secure. Actually, between the three, GitHub has had the most vulnerabilities reported, like that one time someone got administration privileges over the entire website... yet people still trust them somehow. If you're working on government contracted stuff or something like that, where you need perfect and utter secrecy, you could self-host a GitLab instance. Which is $0, compared to GitHub Enterprise.