Easy to integrate with Excellent interface on multiple platforms Free
Integrates well with a lot of developer tools Developer-friendly Clients for every major platform
Open source Can be deployed on premise Faster than Slack
Open source On-premise deployment Free
Open source Great Community Extensive developer documentation
Well-thought Design Mobile friendly Great integrations
Threaded chat Simpler integrations than others, team inbox = awesome Great interface
Free
Mobile friendly Email compatibility Easy to use
KBFS Encypted Git repos End-to-End encryption
Easy to use Minimalist Integrations with CI servers etc
Free Github integration Bitbucket integration
Open source BYOS Docker, Vagrant, NodeJS