IRC is an instant-messaging platform, while Twitter is a microblogging platform that was available to anyone in the pre-smartphone era as it was initially tailored for SMS message length.
IRC requires a client (okay, you could use a web gateway), and you somewhat need to know what you're doing (not saying it's hard, but the average user might not even care about accessing IRC if it requires a minimum of effort), while Twitter could be used through a flip-phone or accessed simply through a web browser, which you can assume everyone have.
IRC is an instant-messaging platform, while Twitter is a microblogging platform that was available to anyone in the pre-smartphone era as it was initially tailored for SMS message length.
IRC requires a client (okay, you could use a web gateway), and you somewhat need to know what you're doing (not saying it's hard, but the average user might not even care about accessing IRC if it requires a minimum of effort), while Twitter could be used through a flip-phone or accessed simply through a web browser, which you can assume everyone have.