Joomla is the best, no difficulty in managing, instal FCK editor, which will give you the option to post article from frontend by registered users, so users themselves can submit articles which comes for moderation by the admin, Use tabs and slides to make the content area flexible if you want, there are countless possibilities with joomla.
they are better cms than jomala for tutorials. http://www.webresourcesdepot.com/category/extras/cms-softwares/
I think joomla can do the job easy Have you tried finding some other CMS specially made for tutorial sites ? if you find one, it may be really helpful.