I am giving a talk next week about using wordpress.com for blogging.
A long list of comparison was found here (updated to 2010):
A discussion is running here:
And also a few people commented on the subject here:
So far, I am not sure I have a strong enough reason the defend WordPress over blogger. If anyone here would be willing to give me strong reasons (either new features that will get unveiled in the near future, or why some points are more important then others) - it would be a huge help.