We are analysing the best tool to test REST APIs. Also considering in mind, integration with TFS.
Some basic starter differences:- Postman is lightweight browser based tool. easy to use, easy to share tests b/w team members by export option,
SoapUI is also easy to use with SoapUI you integrate it with GIT/SVN directly for Checkin and checkout your scripts.
SoapUI supports Groovy Scripting, Postman don't for basic test scenarios you can use postman, if there is a need for logical based decision making calls SoapUI is best.