Social issues make gitlab better although there are also social downsides.

The people who submit fake/AI issues and PRs for resume purposes seem to exclusively use github and this is a substantial expense for the real users (see the recent Curl discussion). Gitlab doesn't have those people (or at least its a wildly smaller problem).

One social downside is noobs will insist a project does not exist if its not on github, even if you send them the gitlab URL. Almost have to physically cut and paste the gitlab URL into their browser for them before they will believe. You can either do nothing which filters them, not a bad idea, or create a clone or placeholder on GH that basically links back to the real repo on GL. I don't know if that is allowed in the ToS for GH but people certainly do it a lot.