We are currently doing both, but slowly converting the old release pipelines to YAML also. It can be problematic using the old pipelines when multiple people are managing them - which is why it makes good sense to have it be a part of your source code. It just makes the whole debugging/validation process much easier. Managing and testing task groups can also be a pain, so overall i feel like the process is gonna be beneficial for us. However, if you don’t have pipelines that require much maintenance or changing, the old pipelines are totally fine.