Google gives preference to Blogger/Blogspot.
Over the years, I've noticed that blogs (and blog posts) on Blogger (blogspot.com) not only get listed quicker on Google than on Yahoo (which is natural since Google owns Blogger/Blogspot, but also get listed higher on Google than other search engines.
I've also noticed that when you post to your blog, its ranking in Google's search results goes higher for a couple days, even the older posts. It's as if Google factors in "time since last post" in their ranking algorythm.
Wordpress seems to be the better blogging platform from a technical perspective, but it sure appears to me that Google plays favorites with Blogger/Blogspot.