Microsoft owns both. If you're picking a CI/CD platform in 2022, the choice between Azure DevOps and GitHub Actions depends on factors that product marketers won't emphasize.
Azure DevOps strengths
Azure DevOps Pipelines has matured faster here. You get better variable groups and pipeline templates in YAML, solid package management through Azure Artifacts, classic release pipelines if you prefer the graphical approval approach, and tight integration with Azure Boards. If you're already living in Azure Boards for agile management, keeping your CI/CD in the same place saves you from context switching all day.
GitHub Actions strengths
Actions lives in your repository. Workflows sit right next to your code, the Marketplace has thousands of community actions, and OIDC for cloud auth is more polished. If you're doing open source or using GitHub for code review anyway, the integration between pull requests and workflow runs just works.
The duplication question
Everyone assumes Microsoft will deprecate one eventually. Officially, both stay. But honestly, the investment has tilted toward GitHub: Copilot, Codespaces, Advanced Security. GitHub Actions is getting more attention. If I'm betting on where Microsoft's heading long-term, it's GitHub as the platform.
Migration considerations
Moving from Azure DevOps to GitHub Actions means: translating your YAML (similar concepts, different syntax), swapping DevOps tasks for Marketplace equivalents, migrating artifacts if you're using them. It's not trivial, but it's not brutal either for most setups. The real question is whether the Actions advantages justify the effort for your workflows.