When comparing Nettalk vs Quassel, the Slant community recommends Quassel for most people. In the question“What are the best IRC clients for Windows?” Quassel is ranked 7th while Nettalk is ranked 14th. 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).
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Can overlay incoming messages
Nettalk can be set up to overlay incoming messages. Especially useful for games.
Pro Built-in spellcheck
Pro Free and open source
Pro Multi-lingual interface
Nettalk is available in English, Spanish, Dutch, Russian, Chinese, Hungarian and German.
Pro Easy interface
Simple and good looking interface.
Pro Encryption support
Pro Scriptable
Pro Functionality can be extended via plugins
Pro Free and open source
Quassal is available for free with source code licensed under GPL and available here.
Pro Distributed
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.
Cons
Con No longer developed
Development ceased some time ago (2012).
Con Poor log management
It stores all logs in one file in a custom format.
Con German language
Is primarily a German language client, so the spell check, etc. is in German.
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.