I love blogging! I've blogged on both Blogger and WordPress over the past 5 years. I'm currently using WordPress.
I started with Blogger, which I would recommend if you want the site to be blog only. It's a very simply to use platform, and very strong for blogging.
I moved to WordPress when I felt that I wanted my site to be more than just a blog, but a full website. WordPress is a little more complicated, but I also find it to be a little more comprehensive, too.
I know you said you didn't want to pay for anything, but I would recommend starting your blog on WordPress.com if you do want to one day move to a paid option. This way, you can familiarize yourself with the WordPress world in case you did want to move to a self-hosted WordPress based site. My site
http://simplystephko.com/ is run on WordPress!
Let me know if you have any questions! I LOVE talking blogging!