IMHO blogdesk and live writer both are good and have their own pros n cons
Blog Desk
Pros
*Ability to crop images and add a few effects such as shadow, frame etc
*Ability to post a blog entry accross multiple blogs in one go (Just select the blogs and categories)
Cons
*Not able to add new categories
Live Writer
Pros
*Ability to crop images and add a few effects such as shadow, frame etc (Add On)
*Ability to add categories on the fly
Cons
*Cannot cross post multiple blogs
Another blogging client I have tried but not been able to use much is
Zoundry Raven
Regards
G