Blogs offer much more freedom, I think. You can submit your own topics, or spins on topics, and you don’t necessarily expect a response (even though it’s often nice to hear from people since you are posting something in the first place). You are just sharing your thoughts and feelings, even if there are some basic guidelines. Discussion boards are more about staying on a specific task, creating threads that purposefully facilitate discussion with others, and assuming response because of the hope of discussion. Depending on the subject matter, discussion boards can be more intimate because they are confined to specific people, while blogs are generally a public format. I feel I write differently in these blogs than I do in discussion threads, though my general voice is the same. I think blogs also might make one feel like they have to think of more to say to make it a meaningful post. It makes me think of my husband, who tends to be quite colorful and dramatic in his choice of words when writing – and he would be more so while blogging, while reigning that in a bit if he was on a discussion board (although it never really goes away – he can make a grocery list sound like a poem!).