I use the short URL on Facebook due to the fact at times Facebook will not display the image of the hub nor the summary, just a link, when you use the longer URL. Should that happen, and it has happened with me and other, the solution is to use the short URL and that has always displayed the photo as well as the summary of the hub.
I also use the short URL when I Tweet at times, depending on how much text that I place prior to the link.
I use various tools besides Twitter to tweet at times. Hootsuite is one and they will shorten the URL if you specify them to do so. However the shortened URL will carry the ow.ly letters in the shortened link where as the HubPages URL will carry hub.me. Just a preference of mine to sometimes show the "hub.me" in some of what I share on Twitter versus the Hootsuite "ow.ly"