The titles you submit are used as the link text (also known as anchor text) with which a directory points to your site. Hence, having multiple titles gives you the advantage of varying your anchor texts to target different search terms or phrases. If all incoming links have the same anchor text pointing to the site, search engines could be suspicious of the authenticity of the links. Hence it is always more beneficial to have multiple titles. In the same way, it would be beneficial to have multiple descriptions with which to submit your site. If all the descriptions were the same, search engines could easily identify that all the incoming links to a website, come with the exact same descriptions. This could be a reason for the search engines to consider these to be duplicate links, artificial links or sponsored links. In order to avoid such suspicion, it is best to vary both the titles and the descriptions so that no two links look like duplicate links.