Wordpress blogs rank better, plus you can get a ton of plugins for it (and host it on your own server/domain name).
It's not the free host (WordPress vs. Blogspot) that determines which is better from an SEO perspective. It's the blog theme you choose at that free host which is going to affect the on-page/on-site SEO friendliness of your site. The search engines don't discriminate or rank pages differently because of which host you chose from the two. It's the blog theme that determines what values get rendered in <title>, <h1>, <h2>s, etc. Off-site SEO is the same for both. But personally, I prefer WordPress because of all of the plugins available some of which are SEO plugins like All-in-One SEO plugin which can help even poorly written themes become more SEO friendly.
everyone agree on wordpress. yes wordpress is better then Blogger but both give great results in SEO.