In Azure DevOps I can schedule an auto merge for a PR when all merge check requirements are met. This is awesome because I can schedule immediately after I posted the PR and only if there are blockers such as comments that needs to be resolved I have to go back to the PR to resolve it. In Bitbucket the Merge button is only enabled once all merge check requirements are already met (other than the build). So I am forced to go back to click the Merge button at some point. Basically the "automatic merging / pending merge" feature in Azure DevOps is much more streamlined than what I've found the one in Bitbucket to be.

"Merge Checks Support

This functionality works alongside merge check requirements, so branches that have required merge checks (such as a required number of approvers, all tasks being resolved, etc.) will have those checks honored. This works by preventing the option the merge if there are any open merge checks, with the exception of successful builds."
Source: https://bitbucket.org/blog/automatic-merging-when-builds-pass