Both of them are usefull for wrtiting posts, pages and blogs. On both of them you can comment in the section below the blogs and in both of them you can decorate your blog.  Because at the end, both of them are websites for creating a blog. But I prefer Blogger than Wordpress because of many reasons.  First of all, Blogger is more popular and easier to find than Wordpress. In Blogger, you feel more comfortable because everything is more organized and you can find the setting you want easier than in Wordpress.  Also, when you are in Blogger, writing a page, post, or anything you want, all the settings you want are visible and easier to find than in Wordpress.  For me, to find the "layout" section on Wordpress was difficult and, unlike Blogger, here it dosen't save your posts or your pages. That's why I prefer Blogger than Wordpress