When comparing KVIrc vs Polari, the Slant community recommends KVIrc for most people. In the question“What are the best IRC clients for Linux?” KVIrc is ranked 7th while Polari is ranked 11th.
Ranked in these QuestionsQuestion Ranking
Pro Plenty of customization options
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.
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 Great UI
The CSD-based UI is great to look at. No screen space goes entirely wasted and is presented neatly.
Pro Easy to use
Polari is very straight forward to use.
Polari integrates nice with GNOME, on a visual and technical level. It uses GNOME online accounts and runs empathy in the background.
Con Some advanced features are lacking
Polari's users will find some advanced features lacking, such as Direct Client-to-Client (DCC).
Con May seem too simple
Unlike Hexchat or other alternatives, it does not expose much of its functionality though some of it might really be present.