blogs are incredibly useful, if you have a group of high pr blogs with regular content on different c class ip's you can work magic...
Blogs has more advantage than site in term of traffic. people go to blog and read it more often than from sites. I dont see any reason why google should treat it less important than a site. Maybe Google might think people pay for adwords to advertise their blogs less than sites pay, and they have to pay lots of money for adsense from blog. but I dont really know.