I currently have a website in which I can add a feature that integrates with Twitter. I can add this as one of the features for a premium plan. Alternately, I can create a brand new website and have the Twitter integration feature be the the primary feature (I believe that this feature will have value by itself)
By adding to the existing website, I get the advantage of all the SEO work done and can leverage on the existing user base. However, if I build a new website, I may be able to get additional revenue.