At first glance, GitLab is neater and clearer thanks to its well-structured user interface, which is why many users say that its handling is simpler and more intuitive. In GitLab, items are not only listed in the list, but can also be organized and managed in a desktop view.
Another big advantage over GitHub is that GitLab's user interface (UI) is scalable and can be flexibly adapted to screen size, while GitHub only offers a fixed standard size. For this reason, in case of visualization on mobile terminals, GitLab is usually the best choice as an alternative to GitHub.
The comparison also reveals that editing and code creation is a bit easier in GitLab, since the tool has an integrated development environment (IDE). Instead, GitHub only has a very minimalist text editor.
Although to be fair, it must also be said that these differences are in the background of the GitLab vs. GitHub if you use the platforms on the desktop and integrate them into third-party editors or IDEs, since, in this case, we hardly deal with the interface itself. Also, if you haven't used either tool yet, you'll have to do pretty much the same familiarization work.