When comparing Google Hangouts vs Mattermost, the Slant community recommends Google Hangouts for most people. In the question“What are the best Skype alternatives?” Google Hangouts is ranked 9th while Mattermost is ranked 15th. The most important reason people chose Google Hangouts is:
Hangouts offers both an Android and iOS app so users can participate from nearly any mobile device in addition to his Desktop.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Mobile support
Hangouts offers both an Android and iOS app so users can participate from nearly any mobile device in addition to his Desktop.
Pro Screen sharing
Any user can share his screen (or only a specific desktop or window) while still continuing an audio conversation.
Pro Free group video support
Hangouts works with up to 10 participants using video out of the box or up to 15 if you are a business, government or school. It determines who is the primary speaker at any given time, and the camera view automatically switches to that user.
Pro Useful for businesses
Hangouts can scale to become a videoconferencing solution for an entire company, since the software can run on nearly all platforms. In fact, Google itself uses Hangouts as its meeting room video conference software.
Pro Easy to start using
Hangouts is integrated with Gmail & Google+, does not require you to download desktop software, and all chats can take place directly in your browser, significantly reducing the barrier to entry for a new user.
Pro Completely free
Google offers all features of Hangouts completely free. There are business, education and government solutions that increase the participant count to for video calls to 15 and offers support.
Pro Cross platform
Hangouts work on Android, iOS, Chrome OS, web and as a Chrome extension.
Pro Live broadcasting and instant recording
With Google+ “Hangouts on Air”, you can broadcast any hangout to an unlimited audience via your Goolge+ Profile or simply a generic YouTube link. Moreover, any Hangout on Air (public or private) is automatically saved as YouTube video that you can keep for private reference or use in any way that you would normally share a YouTube video. This allows you to record conversations without additional obtrusive software.
Pro Google Voice integration
Allows for a fixed phone number, receiving and making calls. Calling US or Canada is free.
Pro Integrates with Google Maps for sharing locations
When chatting with people while trying to plan a meet up, the share map button can be extremely useful.
Pro Android app does both sms and hangouts messaging
Pro Can be self-hosted
You don't need to rely on someone else's servers, you can host Mattermost on your own server.
Pro One-line Docker install
With Docker set up, you can install Mattermost with the following command:
docker run --name mattermost-dev -d --publish 8065:80 mattermost/platform
For other cases, installation instructions can be found here.
Pro Similar to Slack
Almost all features of Slack are available in Mattermost.
Pro Free - OpenSource
You can download and use it as free for self-hosted server.
Pro Mobile apps for android and iOS
Pro You can change theme
Pro Desktop app for MacOS, Linux and Windows
Pro Browser notifications
Pro Mark-Down support
Yes, it supports markdown.
Cons
Con Poor video call quality
Only goes up to 720p30 + low bitrate.
Con Owned by Google
Con Lacking clients for older versions
Con High hardware usage
Con Not recommended for long sessions

Con Won't work on Windows 8-style UI
As Hangouts uses a browser plugin on the desktop and it doesn't work with Windows 8-style UI, it has to be used in desktop mode.
Con No easy End-to-End Encryption setup
Con Features not available out of the box
Difficult to setup the many features it offers. The easy docker installation is for the application only, not it's feature sets. Requires a license for full-set of features.
Con Centralized
Con Poorly made iOS app
Built natively using React it suffers from unresponsiveness, input lag, and sometimes broken services. Coupled with a bad user experience.
Con Poorly made Android app
The Android application is just a badly wrapped web-view which does not perform well and has no form of offline caching whatsoever.
Con Self-Hosted
This doesn't work for every type of company. Mainly great for those concerned with privacy, security, compliance and control of your data/information.
