I'm also in the process of moving from jenkins to gitlab... and until now, the process is pretty smooth and easy ... gitlab-ci is easier to grasp and to work with... the only issues i got is about things like publishing build results (lints check or test results /counts ) althoug there is basic support for artifacts. it's not easily possible (at least for now) to fetch the artifacts for a given commit or branch without doing multiple api calls.

Jenkins 2 pipeline feature didn't look like more then the plugin they had before - but bundled into the core.

We just moved from a Jenkins Pipeline-setup to GitLab, didn't take that long time and our builds started going a lot faster after that.

The hint was very obvious.