Exactly, I do believe that having a personal blog is good, but not especially for writing, thus i don't prefer or suggest anyone to write on your personal blog because the data you get on your personal blog could take too much time. (maybe years) on the other hand, on social blog you can get instant feedback of your work. Also you can redirect/monetize your social blog audience to an email newsletter and i think this is great way to backup of your audience. On top of that your personal blog should be for your businesses purpose not for writing.