I think GitHub are doing well, but one cannot deny that GitLab has carved out a fantastic niche (on-prem, private instances, OSS, etc) that GitHub doesn't compete in. So while I agree GitHub are "the" company to beat, I think GitLab is doing a good job of contrasting. PS - No affiliation with anyone.
That only really leaves the fact that its OSS that differentiates Gitlab in your list. Not comparing the two, just making sure you're aware.