When comparing KVIrc vs Smuxi, the Slant community recommends KVIrc for most people. In the question“What are the best IRC clients for Windows?” KVIrc is ranked 8th while Smuxi is ranked 15th.
Ranked in these QuestionsQuestion Ranking
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 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 Extensive documentation available
Help files and online resources show all of the feature and scripting capabilities.
Pro Twitter integration
It's possible to check and interact with Twitter's timeline, replies and direct messages from the Smuxi client.
Smuxi offers an option to keep idling in a channel even when all front-end clients are closed. It's possible for a front-end client or multiple front-end clients to connect to a single server. This allows setting up an always on-line server that can be accessed from anywhere.
Pro Plugins and scripts can be written in any language
Pro Highly customizable interface
Pro Facebook chat, gTalk and Jabber integration
Smuxi has XMPP protocol support that allows integrating with Facebook chat, gTalk and Jabber.
Pro Theming support
Pro Caret mode
Caret mode allows navigating through messages (the output buffer) via keyboard.
Con Poor script and plugin library
Smuxi's script and plugin library contains less than 10 entries.