How should I insulate a bedroom in the attic?
The picture isn't really two different methods, but two different plans.  It's one method (soffit at the bottom and ridge at the top).  The only difference is what you actually insulate - and it's the same thing.  Insulate anything that you want kept at "livable" temperature, since it will be part of the conditioned envelope of the house, keeping in mind that the larger you make that area, the more heating and cooling you're doing.  We did a blog post on this subject as well, check out http://diy.blogoverflow.com/2011/12/resuscitating-the-roof-providing-adequate-roof-ventilation/