I would use the blog to broadcast information, share perspectives, or tell a story. Students then will be commenting on the the posts.
I would use the wiki for everything else:) Anything that requires collaboration between student and teacher, teams and teams, or information that will be edited and contributed by multilple members.
Lieumarg, I do use both in my trainings, but I usually do more with a wiki than the blog. I have started using the group feature in the Engage Community and it has been great. The teachers only have one login and they have access to everything, including the blog and discussion features. The teachers upload their unit plans, etc via a discussion and it works great.
Hope this helps,
Excellent question. From my experience I know teachers who have little knowledge of blogs and wikis are surprised at how these tools can benefit students. The teachers see how blogs can be used in class. When teachers see the possibilities of a wiki, they are generally very impressed. My principal was so impressed with wikis that he had our entire staff using a wiki to collaborate this year. The results of this collaboration have been outstanding. Some of our less "tech-savvy" teachers use the wiki without reminders or assistance.
My suggestion, therefore, would be to use a wiki as much as possible. If you are going to include blogs I would ask your teachers to create blog posts about content or the Intel Teach program. This will give the teachers an opportunity to reflect on their learning. Teachers could put their blog URL on the wiki and a short description of the feedback that would benefit them most.