I think it is easiest to post on a forum since all you need to do is login, and press the reply or new topic button, and start posting.
While with a blog and CMS, you need to login, open up the post editor, and write your post. Sometimes, you also need to make a link on the front page and navigational sidebar, so users can find your new post easily.
Wordpress and Blogger are also very easy to post on. They can also be easier to post on since you do not have to browse to a section to post in the correct section like Forums, all you do is type tags, and check categories for organizing your posts.
Forums are pro. I don't really post much anymore, since my life is REALLY busy, it's hard to make time for multiple places to talk. So I just try to stick to a couple forums.
I prefer a forum above all else, you can have all of the add ons and bells and whistles to your blog, website or cms to duplicate the posting ui of a forum, and it still wouldn't come close.
For posting, I prefer forums, and I accept no imitations..
Definitely blogs (particularly WordPress). You have the big editor with all of your buttons in one place (images, tagging, categorizing), and there's also an auto-save feature that saves what you're typing as your going so if your computer crashes or shuts down you have a backup of what you were typing.
Blogs like wordpress are kinda easy 
