When comparing Colloquy vs Adium, the Slant community recommends Colloquy for most people. In the question“What are the best IRC clients for Mac?” Colloquy is ranked 3rd while Adium is ranked 7th.
Ranked in these QuestionsQuestion Ranking
Pro Free and Open Source
Pro Nice Native Design
Colloquy was designed with the Mac OSX interface conventions in mind, so it's got a native look and feel.
Pro Plenty of advanced features.
Colloquy has many of the features an advanced user would need such as file transfer support, and even support for mIRC colors. It supports scripting via AppleScript.
Pro Supports SILC and ICB.
Pro Mobile version.
Colloquy also has an iPhone version for IRC on the go with many of the same features.
Pro Easy-to-use interface
Pro Open source
Pro Supports file transfers
Pro OTR encryption
Con No longer supported
The app will not work on the latest releases of OSX as it has not been updated since 2014.
Con No way to search chat logs within Colloquy
Chat logs are not viewable within the app. You must go to the directory and open the file with a text editor.
Con Appears to be abandoned
Not Gatekeeper-compatible, SSL cert expired, social media presence is ancient.
Con Lack of multi-resource message capability
No carbon copy, for example.
Con Lack of OMEMO encryption
the de facto standard for Jabber Texting [xmpp]
Con No antispam (built-in or by plugin)
It has no challenge-like antispam (such as seen on github.com/jesobreira/box-sentry plugin for pidgin).