For me, I could have gone either way but I chose to create a blog.
I provide information with very little additional features, such as forms, so a blog made a lot of sense. I also find updating to be very easy since blogs are designed for those with limited HMTL experience.
If you would like to include more functionality with your idea, such as forums, multiple forms (almost like a Web app) then definitely go the Web site route.
Then again, to make it even more confusing, you can create a Web site and complement that site with a blog, like Lisa has done. In this case they can both share the same domain, just that the Web site would be use the
www.yoursite.com and the blog could use blog.yoursite.com.