If Facebook launched today, Twitter wouldn’t die. Twitter has a very loyal following and serves a purpose that Facebook doesn’t – just as Facebook serves a purpose Twitter lacks of.
Every time you have to wait 30 seconds for a 6 second video to buffer; a kitten dies. Every. Single. Time. And in the Vine world, that is a shit load of kittens.
Now the good thing about this is that Vine/Twitter can totally fix this by boosting their servers. They already prioritize the popular accounts by faster buffering, but it is time to set the prioritizing to more general so it´s easier to explore more unknown accounts.
Instagram´s biggest advantage is Facebooks crazy NASA-like servers that are blazingly fast. Other then that, it´s fair game for them both.