GitHub offers Free Trial, but Postman does not.
GitHub is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Postman is designed for Large Enterprises, Medium Business and Small Business.
Pricing for GitHub Starts at $4/User/Month whereas for Postman Starts at $12/User/Month when Billed Yearly.
Some top alternatives to GitHub includes LiveCode, Codeanywhere, Visual Studio IDE, CodeinCloud, GitLive, Microsoft Azure, GitLab, CodeSee and Bitbucket.
Some top alternatives to Postman includes Apigee Edge, WSO2 API Manager, SwaggerHub, API Fortress, BlazeMeter, TestMace, Insomnia CLI, Meta API, RestCase and Dapi.