When comparing Google Allo vs Discord, the Slant community recommends Discord for most people. In the question“What are the best messaging apps for Android?” Discord is ranked 13th while Google Allo is ranked 22nd. The most important reason people chose Discord is:
Discord follows the same type of interface design popularised by Slack, which is extremely clean and attractive, and doesn't clutter the interface with unnecessary chrome and cruft.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Integrated with Google Assistant
Automatically shows options for restaurants/movies/etc when relevant according to the context of the conversation. It's also able to perform actions accordingly like order tickets.
Pro Supports end to end encryption
You can send end to end encrypted message that will auto-delete themselves after a specified time.
Pro whisper SHOUT let's you express yourself through text size
You can easily adjust the text size to show either a whisper or a shout, adding emphasis to your messages. Simply hold the send button and slide up (to shout) or down (to whisper).
Pro Message can self-destruct after a certain time
You can send end to end encrypted message that will auto-delete themselves after a specified time.
Pro Animated stickers and emoji
Some shouted emoji animate and you can download additional stickers and send animated stickers.
Pro Full resolution picture sharing
Pro Smart replies
Part of the Google Assistant is providing common answers based on your conversation thread (like in Gmail/Inbox).
Pro Themes
Each chat's theme can be changed to one of a few themes. Some themes even have specific chat colours for each user, making it easy to see who is talking.
Pro Can share a location
Share your current location or any place with other people.
Pro Encryption on-the-wire and in cloud storage
All messages are encrypted while in transit and on Google's servers.
Pro File sharing
Pro User friendly
Discord follows the same type of interface design popularised by Slack, which is extremely clean and attractive, and doesn't clutter the interface with unnecessary chrome and cruft.
Pro Free for unlimited users
Unlimited amount of users.
Pro Can be used in browser
Users can invite others to join a Discord channel via a web link, which means no installation is required to use the software - which is one of the big typical barriers to entry for social software.
Pro Good 1-click invite system
Discord allows inviting people to a specific channel with a link. Links can be set to expire. Low effort/passive invite mechanics.
Pro Easy setup
You can quickly send invites to people and they can join in using the web client without having to create an account or install the app.
Pro Has low-latency VoIP support
Pro Supports video and text communication
Behaves and looks like Slack for regular text channels, but with the ability to create voice channels as well
Pro Numerous controls for setting member roles.
Deny access, Deny write message, Allow read messages etc.
Pro Ability to create bots
Discord provides an API for creating custom bots.
Pro Open source bots and management tools
Discord has a wide variety of bots for things from airhorn noises to automated server management, to leveling systems for chat. The bot API is open and there are dedicated sites for finding bots.
Pro Game integration
Discord shows which game each user is currently playing, which among other things helps users to form PUGs with minimal hassle.
Pro Dark theme out of the box
Pro Familiar for Slack users
For those that are used to the way Slack (a similar chat client) works, Discord will be familiar in its use, which lowers the learning curve quite a bit for those that have switched or tried Slack before.
Pro Low effort invite mechanics
Pro Android app has push notifications
Pro Syntax highlighting and Markdown support
The support is limited but still exists. It's a killer feature for dev teams.
Pro DDoS mitigation
Discord prevents users from being DDoSed out of games.
Pro Targeting of roles
Targeting roles allows for quickly requesting someone from a group e.g. artist, moderator, etc.
Pro Ability to thread channels
Ability to create channel categories for channels to sit inside of.
Pro Friendly payment policy
Free account have no tangible restrictions.
Premium account is just a way to say "thank you" to developers. And it work for all servers of discord (not as in slack). And it can be purchased by one who wants. In contrast to Slask, where all active members of the server should be "premium".
Pro Language localization
Have localization for many language, including Russian.
Pro Does not allow NSFW related things to be posted unless in a NSFW channel
Cons
Con No web interface (yet)
Currently there is no web interface to send message using your computer. Project leads have teased screen shots of the web interface.
Con Few users currently
Allo was just released in September, 2016 and it doesn't have a very large following yet. We haven't yet seen how popular it's going to be.
Con Exclusive
If your contacts aren't on Allo it is worthless, and no one is on Allo. Tried it after Hangouts fail, discarded it within days.
Con History deletes on sign in
If you uninstall the app or migrate to a new phone your messages history is deleted. This, despite the fact that Google keeps a copy of your messages permanently for data crunching.
Con Single device
Part of reliably saying if one saw your message, and having it tied to a phone number, is that you cannot have the same Allo account on two phones.
Con Proprietary software
Discord is closed-source, meaning their code isn't available for inspection or reproduction
Con Based on Electron = eats a lot of ram
Con Some functions cut out and available only with "Nitro" subscription
Con Developer's previous company was sued for privacy violations, among other things
See:
http://classactionlawsuitsinthenews.com/class-action-lawsuit-complaints/openfeint-green-international-privacy-class-action-lawsuit-complaint/
https://www.ftc.gov/enforcement/cases-proceedings/closing-letters/openfeint-inc
Discord's privacy policy also states that while they might not sell your data, a company they get sold to will quite possibly attain said data and thus may be in "more" shady hands.
Con No self-hosting avaliable
Discord is wholly hosted by Discord (the company), you cannot run private instances, and all servers are hosted on their infrastructure. For most people, this won't really impact their usage.
Con Not a generic "team chat" tool
All the UI and the features are aimed specifically at communicating with your gaming team/clan.