I'm not that familiar with Github but the workflow for creating issues, trying branches to that issue, and tying pull requests to an issue was very good and really helped me get started with Gitlab. I also appreciated the build server which is very integrated into that workflow. I tried creating my own project on Github but couldn't really figure out how to tie a pull request or a branch to an issue. I'm sure it's possible but with Gitlab it was immediately obvious how to do it and almost hard to avoid it.

I spent a lot of time with Gitlab Auto DevOps but never really got it off the ground. I think I could make it work now but that Git + Gitlab + Docker + Kubernetes was just too much to learn in one go. It certainly didn't help that I started out with Amazon EKS instead of the recommended Google Cloud option.

In the future I would like see them add a hosted Maven repository (but I don't think that's in the stars) and if they are feeling adventurous I would like to see them explore visualizing the execution of multi-stage Dockerfiles as process pipelines the way they visualize .gitlab-ci.yml files today.

Perhaps these very subjective impressions from someone who doesn't have a lot of prior experience with either product will give you an idea of how these products differ. ;-)