When comparing Communi vs Quassel, the Slant community recommends Quassel for most people. In the question“What are the best IRC clients for Linux?” Quassel is ranked 5th while Communi is ranked 13th. The most important reason people chose Quassel is:
Quassal is available for free with source code licensed under GPL and available [here](http://bugs.quassel-irc.org/projects/quassel-irc/repository).
Ranked in these QuestionsQuestion Ranking
Pro Elegant and minimalist interface
Communi user interface for desktop and mobile is minimal, which helps you focus on the task at hand instead of being distracted by extra UI elements.
Pro Good ZNC integration
The author is involved in ZNC development, so the latest ZNC goodies are guaranteed to be well supported (http://communi.github.io/znc/). With help of the documented ZNC modules, Communi retains its state well across sessions. No repetitive buffer playback on reconnect, notifications and banners for newly received messages only, queries stay open until closed etc.
Pro UI runs on multiple platforms
While Communi itself is a IRC framework, the project offers several UI implementations such as desktop, SailfishOS, Meego and Symbian.
Pro Quassel protocol implementation
Communi is integrated with Quassel.
Pro Event merging
Consequent events (joins, parts, quits etc.) are merged to reduce noise and to keep focus on the discussion.
Pro Free and open source
Quassal is available for free with source code licensed under GPL and available here.
It's possible for a front-end client or multiple front-end clients to connect to a single core client. This allows setting up an always on-line core that can be accessed from anywhere.
Pro Easy installation on Ubuntu due to the existence of PPA's
Right now Quassel has a PPA maintainer, which allows you to install the stable version or daily versions.
Support for PostgreSQL as database backend and easy to configure for people that know a bit about systems.
Con No DCC
Communi does not support DCC (for a reason)
Con No scripting
Communi has no support for scripts
Con Potential memory bloat in monolithic client if left running for a period of time
(I don't know if this problem has been fixed in recent years, but I have doubts)
Con No DCC support
DCC or Direct Client-to-Client protocol allows for private communications between users (without the traffic being routed through servers). Neither chat nor file transfers are supported.