When comparing GroupMe vs Element (formerly Riot), the Slant community recommends Element (formerly Riot) for most people. In the question“What are the best messaging apps for Android?” Element (formerly Riot) is ranked 2nd while GroupMe is ranked 23rd. The most important reason people chose Element (formerly Riot) is:
You're not confined within Element's or even Matrix garden, and you don't have to make users of other networks switch to Matrix.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Reads receipts
GroupMe has a built in function to read receipts.

Pro Great web client
GroupMe has an excellent web client that can be used to send and receive messages and manage groups from the desktop.

Pro IFTTT Integration
Allows sending messages from web services via IFTTT.

Pro Integrated calendar
It's possible to add location and time with reminders directly in the GroupMe app.

Pro Makes it easy to silence 1 or all groups
GroupMe has settings that allow muting a single group or turn off all GroupMe notifications from within the app.

Pro Does not require everyone in the group to have a smartphone
GroupMe can set up a custom phone number which allows people without the App to send and receive messages. This makes it easy to add anyone to messaging.
Pro Bridges to other networks
You're not confined within Element's or even Matrix garden, and you don't have to make users of other networks switch to Matrix.
Pro Markdown support
Code snippets in chats can be highlighted with Markdown.
Pro Simple interface
Element has a very simple interface, adding the ability for more inexperienced users to use it.
Pro VOIP and Videoconferencing
Pro Supports encryption
Element allows for fully encrypted text, voice, and video chatting.
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 Element.
Pro Decentralized
An open network for secure, decentralized communication.
Pro Self-hosting and federated network
Pro Libre/open source
Pro Search
Search messages in your current room, or all the rooms you're in. Not subject to a message history limit like Slack.
Pro Cross platform
Web browser
Linux
OS X
Windows
Android
iOS
Pro Large existing community
With public rooms for many people, and you can create your own and let people from the community join.
Pro Etherpad real-time document collaboration
An easy to activate integration that allows multiple authors to edit a document simultaneously.
Pro File Sharing
Pro Supports text, voice, video
Cons
Con Drains battery fast
GroupMe, in order to have a constant connection which allows for notifications drains the battery of a device quickly, which is not ideal for a messaging app that one needs on time notifications from.
