When comparing KVIrc vs irc.c, the Slant community recommends KVIrc for most people. In the question“What are the best IRC clients for Linux?” KVIrc is ranked 7th while irc.c is ranked 15th.
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 Single server
Each instance of the client can only connect to one server and then you can join multiple channels with the join command.
Example: "irc -s irc.freenode.net", then "j #lua" and "j #chicken"
The source code (a single C file) is under public domain.
Pro Infinite scrollback
You can move up and down the history with the "Page Up" and "Page Down" keys.
Pro Automatic reconnection
It automatically connects you back if you happen to get disconnected.
Its website and README do not give enough information about shortcuts and commands. You have to look those things up in the source file.