GitLab CI is extensible through an API.
Built for containers and Docker
GitLab ships with its own Docker container registry, Docker CI Runner and is ready for a complete CI/CD container workflow, while Jenkins requires you to install, configure and maintain additional plugins to create a similar workflow.
GitLab CI/CD is Cloud Native, purpose built for the cloud model. GitLab ships with Red Hat OpenShift and Kubernetes support out of the box.
Container debugging on any environment
Easily debug your containers in any of your environments using the built-in GitLab Web Terminal.
GitLab ships with Prometheous allowing you to monitor the performance of your deployed environments without any addtional setup.
Integrates with Cycle Analytics
GitLab CI integrates with GitLab Cycle Analytics allowing you see how much of your cycle time from idea to production is spent on development, testing and review.
Preview your changes with Review Apps
With GitLab CI you can create a new environment for each one of your branches, speeding up your development process. Spin up dynamic environments for your merge requests with the ability to preview your branch in a live environment.
Comprehensive pipeline graphs
Pipelines can be complex structures with many sequential and parallel jobs. To make it a little easier to see what is going on, you can view a graph of a single pipeline and its status.
With GitLab CI you can upload your job artifacts in GitLab itself without the need of an external service. Because of this, artifacts are also browsable through GitLab's web interface. Travis CI relies on having an AWS S3 account in order to upload artifacts.
Support for Canary Deployments monitoring
GitLab Enterprise Edition Premium can monitor your Canary Deployments when deploying your applications with Kubernetes.
Scheduled triggering of pipelines
You can make your pipelines run on a schedule in a cron-like environment.