Well, I think Sleeping Beauty knows alot more about Tumblr than I do, but I think a blog might do better on either Blogger or Wordpress, if you're looking for a wider audience....
Tumblr is younger and feels more specialized. Alot of folks don't know about it. Some aren't comfortable with the interface, it's not as intuitive as a blog.
In terms of Blogger vs. Wordpress, alot of people perfer Word press, because it's more customizable(although more tecnical) and people can reply more easily to each other.
Personally, I like Blogger because it's easier. More accessible and easier to set up. I find it easier to navigate. But that's just me.
You could visit some WordPress blogs, and see what you think.
Good luck with your decision.