When comparing Yammer vs Riot, the Slant community recommends Riot for most people. In the question“What is the best team chat software?” Riot is ranked 6th while Yammer is ranked 23rd.
Ranked in these QuestionsQuestion Ranking
Pro User interface is modelled after Facebook
To make it easier to learn for new users and increase adoption.
Pro Hashtag support
Hashtags help organize projects and parts of projects easily. Great for getting an overview of a specific subject and seeing if something's missed.
Pro A complete social network for business
Yammer works like a typical social network with status updates, comments, file sharing, groups, etc.
Pro Web and mobile (iOS, Android) versions available
Pro Supports text, voice, video
Integrates with Jitsi for multi-party video chats
Pro Uses Matrix, the open communications protocol
Pro Very good and simple interface
Riot has a very simple interface, adding the ability for more unexperienced PC-Users to use it.
Pro Widgets support
Want to watch that flick at YouTube and discuss it at the same time? Have Grafana graphs stacked above your DevOps team chat? Collaboratively edit Google Docs and chat over without switching applications? This is possible with Riot.
Pro Bridges to other networks
You're not confined within Riot's or even Matrix garden, and you don't have to make users of other networks switch to Matrix.
Con Lacks customization options
Con Still in active yet early development
There is clearly a User Experience issue esp. in web version which the developers are aware of and are working hard to improve. They've got the concept concrete, so UX won't be an issue in no time. Most often used parts are functional, but some are yet not.
The success of riot depends on how fast the development is, or it'll get outdated too quickly as developers of Signal and Telegram have predicted.