I do recommend emacs though. It is not the greatest editor, but it is an amazing experience. It is such an amazing experiment, that has an extensive set of different ways of looking at content and code - it will change how you think about coding.
org-mode is awesome for many reasons, but the similarities/overlap with markdown are an incidental benefit. I wouldn't learn org-mode for that reason, however there are many other good ones that make it worthwhile. I've been using it for years for my own project management, tasks tracking, notes and many other things - it's one of those rare tools that can do many things incredibly well.