When comparing KVIrc vs Colloquy, the Slant community recommends Colloquy for most people. In the question“What are the best IRC clients for Mac?” Colloquy is ranked 3rd while KVIrc is ranked 8th.
Ranked in these QuestionsQuestion Ranking
Pro Still active developement
Despite whats been said, development has been continuing at a steady pace on version 4.3.1 and more recently 4.3.2.
Pro Plenty of customization options
KVIrc does not need to be installed. It can be kept on a flash drive and run from there.
Pro Extensive documentation available
Help files and online resources show all of the feature and scripting capabilities.
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 Works on macOS Mojave
Although not supported anymore, it's been confirmed to work on Mojave.
Pro Has pretty themes like iOS "bubbles"
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.
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.