It has federation so you can talk with people or rooms on other servers. There is also voice and video chat supported by matrix but I'm not sure if conduit has that yet. Also smaller things like picture and emoji support. Irc is a much simpler protocol so you give up a lot of functionally over matrix. In the end just pick whichever one has the people you want to speak to or set up a matrix bridge to irc and speak to people on both if you don't mind self hosting