Blog posts are considered "weak" when the word count is very low (<400). This is because there is less chance to rank in the SERPs, and because it's hard to cover complex topics. However, short blog posts can always be expended in the future.
On the other hand Tweets and Tweetstorms from influential accounts can be very powerful, as they are easier to discover and share. They can also be embedded in blog posts. As such, Twitter may work best for short-term awareness campaigns while blog posts can benefit a startup's digital presence in the long-term.