Twitter can serve as a replacement for a subset of RSS functionality, but even allowing for Twitter to grow that subset, the biggest difference is architectural

Twitter can serve as a replacement for a subset of RSS functionality, but even allowing for Twitter to grow that subset, the biggest difference is architectural: Tweets all run through twitter.com and your ability to retrieve the tweets you want or for the content owners to provide the information they wish depends on Twitter's continued willingness to provide the tools and/or API to do so and to allow you both to keep your accounts. Even assuming they will always want to facilitate this sort of thing and that neither you nor the content owners will do something to get kicked off Twitter, you can be sure that the tools and API will change relatively rapidly over the years ahead. Meanwhile RSS is (usually) hosted on the content owner's server. The format has been stable for 15+ years at this point. Tools that worked for aggregating and dealing with RSS in 2000 still work today. And only your ISP could potentially stop you from retrieving the content you wish, when you want it, how you want to.