"I firmly believe Dynamo could be used for many many purposes, and addin-like behavior is one...
Definitions are easy to share and update. Users can tune them with only some basic Dynamo skill. It is not the same with addins. It is a lot of work to manage and deploy. And users will not be able to tune things. Same thing for macros."
API or not API: addins vs Dynamo in Revit | AEC, you and me.