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).

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 recommend Postman because it's easy to use with history option. Also, it has very great features like runner, collections, test scripts runners, defining environment variables and simple exporting and importing data.