From a StackShare Community member: "I just started working for a start-up and we are in desperate need of better documentation for our API. Currently our API docs is in a README.md file. We are evaluating Postman and Swagger UI. Since there are many options and I was wondering what other StackSharers would recommend?"
I use Swagger UI because it's an easy tool for end-consumers to visualize and test our APIs. It focuses on that ! And it's directly embedded and delivered with the APIs. Postman's built-in tools aren't bad, but their main focus isn't the documentation and also, they are hosted outside the project.
I use Postman because of the ease of team-management, using workspaces and teams, runner, collections, environment variables, test-scripts (post execution), variable management (pre and post execution), folders (inside collections, for better management of APIs), newman, easy-ci-integration (and probably a few more things that I am not able to recall right now).