When comparing Instagram Direct vs Riot, the Slant community recommends Riot for most people. In the question“What are the best messaging apps for Android?” Riot is ranked 1st while Instagram Direct is ranked 44th.
Ranked in these QuestionsQuestion Ranking
Pro Video & photo messages
Photos have to be cropped to be square.
That can be applied to photos and videos.
Pro Group messages
With up to 15 people.
Pro Uses Matrix, the open communications protocol
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.
Pro Supports text, voice, video
Integrates with Jitsi for multi-party video chats
Pro Web and mobile (iOS, Android) versions available
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.
Con Walled garden
Can't communicate with people outside of Instagram.
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The success of riot depends on how fast the development is, or it'll get outdated too quickly as developers of Signal and Telegram have predicted.