Hubpages has a lot of authority with Google because of its PR 6 rating.Therefore, it's easier for your Hubs to rank on the search engines if you optimized your hubs for the right keywords than creating brand spanking new blog pages with no authority.
Keep in mind, however, that if your Hubscore is lower, your links are considered nofollow. In other words, your links will get no link juice for backlinking until your Hubscore increases. I can't remember the count: 80 or 85 and up? You have to check.
Hubpages did that on purpose to keep people from spamming and putting cruddy content up. If everyone did that, Hubpages could lose its high PR status. It's to get us to write better quality content.
You can check if links are nofollow or dofollow by downloading the free Firefox plugin called NoDoFollow Plugin. Then turn it on.
Pink = nofollow
Purple = dofollow