User blog comment:Dopp/Technical Update: May 17, 2011/@comment-3104099-20110523043706/@comment-1997905-20110523200831

They both have strengths and weaknesses. IRC, generally speaking, is the better choice, as it's much more flexible. Chat, on the other hand, has the advantage of being able to link with wikitext, and will probably have some other wiki-related features added on later. Like most things with Wikia, Chat and IRC will be used by newer users and experienced users respectively. IRC will not be abandoned when Chat's bugs are fixed.

Furthermore, Chat's interface isn't better than IRC's - Chat's interface is only prettier. The chat interface does much less than the IRC interface, and wastes an annoying amount of space.