The Tumblr blogging platform allows you to post text, images, music, videos, and links with ease. Tumblr's used for more of a sharing site, however, where users tend to re-post articles and images, rather than directly commenting on them. Tumblr offers a "like" button, too, which allows you to express interest in any particular post.
Wordpress doesn't really work like that at all. First of all, the Wordpress dashboard is more complex and allows for a lot more customization. If you're looking to do more text-based posts (reviews, editorials, etc.), then Wordpress might be the best option for you. The site also allows you to see how many people are reading your posts and visiting your blog, which is hard to gauge on Tumblr.
Their both great blogging sites, but very different when it comes to sharing information. As I mentioned in the thread, perhaps you want to create an account on both sites to see which one you enjoy more.