Hi Jef,
As a GitHub / GitLab user I really like the idea of moving over (or mirror) to GitHub. Let me share my personal experiences with the GitHub system.
- Merge requests and forks can be easily made, managed and tracked with it.
- Most CI tools (if you use them) all have a seamless integration with GitHub.
- The wiki pages can be created online and also as a separate repo, these are ll written in markdown
- If you don't like markdown you can use GitHub Pages, with which you can commit static HTML, CSS, JS files to a github repo which is accessable with a browser.
I hope my personal experience with GitHub might help you made an informed discussion.
Vincent